diff --git a/codechef/apr18-div1/chefat.cpp b/codechef/apr18-div1/chefat.cpp
new file mode 100644
index 0000000..2f13fdd
--- /dev/null
+++ b/codechef/apr18-div1/chefat.cpp
@@ -0,0 +1,54 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+typedef long long ll;
+typedef vector<int> vi;
+typedef vector<ll> vll;
+typedef pair<int, int> ii;
+typedef vector<ii> vii;
+typedef set<int> si;
+typedef map<string, int> msi;
+
+#define rep(i, a, b) \
+for (int i = int(a); i < int(b); i++) // a to b, and variable i is local!
+#define TRvi(c, it) \
+for (vi::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRvii(c, it) \
+for (vii::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRmsi(c, it) \
+for (msi::iterator it = (c).begin(); it != (c).end(); it++)
+#define INF 2000000000 // 2 billion
+#define mod 1000000007
+
+int main() {
+    ll t,n,q,i,j,l,r,type;
+   	cin>>n>>q;
+    
+    double P[q],ans,T;
+    rep(i,0,n)
+    {
+    	cin>>P[i];
+    }
+    cout<<setprecision(8);
+    while(q--)
+    {
+    	ans = 1.0;
+    	cin>>type;
+    	if(type == 0)
+    	{
+    	   	cin>>l>>r;
+    		rep(i,l-1,r)
+    			ans *= (1-P[i]);
+			cout<<ans<<"\n";
+		}
+		else
+		{
+			cin>>l>>r>>T;
+			rep(i,l-1,r)
+    			P[i] *= T;
+		}
+    }
+    
+   
+	return 0;
+}
diff --git a/codechef/apr18-div1/chefpar.cpp b/codechef/apr18-div1/chefpar.cpp
new file mode 100644
index 0000000..835e3f2
--- /dev/null
+++ b/codechef/apr18-div1/chefpar.cpp
@@ -0,0 +1,119 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+typedef long long ll;
+typedef vector<int> vi;
+typedef vector<ll> vll;
+typedef pair<int, int> ii;
+typedef vector<ii> vii;
+typedef set<int> si;
+typedef map<string, int> msi;
+
+#define rep(i, a, b) \
+for (int i = int(a); i < int(b); i++) // a to b, and variable i is local!
+#define TRvi(c, it) \
+for (vi::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRvii(c, it) \
+for (vii::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRmsi(c, it) \
+for (msi::iterator it = (c).begin(); it != (c).end(); it++)
+#define INF 2000000000 // 2 billion
+#define mod 1000000007
+//logarithmic expo
+ll power(ll x, ll y)
+{
+    ll val=1;    
+    x = x%mod;
+    while(y>0)
+    {
+        if(y&1)
+        {
+            val = (val*x)%mod;
+        }
+        y = y>>1;
+        x = (x*x)%mod;
+    }
+    return val;
+}
+ll spf[1000001];
+bool prime[1000001];
+
+void genprime()
+{	   
+	int i,j;
+    rep(i,0,1000001)
+    	prime[i] = true;
+    prime[0] = prime[1] ;
+    for(i = 2;i<1000001;i++)
+    {
+    	if(prime[i])
+    	{
+    		for(j = 2*i;j<1000001;j+=i)
+    		{
+    			prime[j] = false;
+    		}
+    	}
+    }
+}
+
+void genspf()
+{
+	 spf[1] = 1;int i,j;
+     for ( i=2; i<1000001; i++)
+         spf[i] = i; 
+   
+     for ( i=4; i<1000001; i+=2)
+        spf[i] = 2;
+ 
+    for ( i=3; i*i<1000001; i++)
+    {
+        if (spf[i] == i)
+        {
+            for ( j=i*i; j<1000001; j+=i)
+ 			{
+                if (spf[j]==j)
+                    spf[j] = i;
+            }
+        }
+    }
+    /*for(i=1;i<100;i++)
+    	cout<<spf[i]<<" ";*/
+}
+
+vector<ll> factorise(ll n)
+{
+	vector<ll> ret,ret1;
+	while(n!=1)
+	{
+		ret.push_back(spf[n]);
+		n/=spf[n];
+	}
+	ret1.push_back(ret[0]);
+	rep(i,1,ret.size())
+	{
+		if(ret[i] != ret[i-1])
+			ret1.push_back(ret[i]);
+	}
+	return ret1;
+}
+
+int main() {
+    ll t,n,i,j,k,m;
+   	cin>>n>>m>>k;
+    	ll A[n], P[m];
+    	rep(i,0,n)
+    	{
+    	    cin>>A[i];
+    	}
+    	rep(i,0,m)
+    	{
+    	    cin>>P[i];
+    	}
+    	rep(i,0,n)
+    	{
+    	    cout<<A[i]+k<<" ";
+    	}
+    	
+ 	
+	return 0;
+}
diff --git a/codechef/apr18-div1/cutplant.cpp b/codechef/apr18-div1/cutplant.cpp
new file mode 100644
index 0000000..31a9e8c
--- /dev/null
+++ b/codechef/apr18-div1/cutplant.cpp
@@ -0,0 +1,233 @@
+#include <bits/stdc++.h>
+#include <sstream>
+
+using namespace std;
+
+typedef long long ll;
+typedef vector<int> vi;
+typedef vector<ll> vll;
+typedef pair<int, int> ii;
+typedef vector<ii> vii;
+typedef set<int> si;
+typedef map<string, int> msi;
+
+#define rep(i, a, b) \
+for (int i = int(a); i < int(b); i++) // a to b, and variable i is local!
+#define TRvi(c, it) \
+for (vi::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRvii(c, it) \
+for (vii::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRmsi(c, it) \
+for (msi::iterator it = (c).begin(); it != (c).end(); it++)
+#define INF 2000000000 // 2 billion
+#define mod 1000000007
+//seg tree rmax, rmin
+struct node
+{
+   ll minimum;
+   ll maximum;
+};
+
+ll getMid(ll s, ll e) {  return s + (e -s)/2;  }
+
+struct node MaxMinUntill(struct node *st, ll ss, ll se, ll qs,
+                         ll qe, ll index)
+{
+    // If segment of this node is a part of given range, then return
+    //  the minimum and maximum node of the segment
+    struct node tmp,left,right;
+    if (qs <= ss && qe >= se)
+        return st[index];
+ 
+    // If segment of this node is outside the given range
+    if (se < qs || ss > qe)
+    {
+       tmp.minimum = INT_MAX;
+       tmp.maximum = INT_MIN;
+       return tmp;
+     }
+ 
+    // If a part of this segment overlaps with the given range
+    ll mid = getMid(ss, se);
+    left = MaxMinUntill(st, ss, mid, qs, qe, 2*index+1);
+    right = MaxMinUntill(st, mid+1, se, qs, qe, 2*index+2);
+    tmp.minimum = min(left.minimum, right.minimum);
+    tmp.maximum = max(left.maximum, right.maximum);
+    return tmp;
+}
+ 
+struct node MaxMin(struct node *st, ll n, ll qs, ll qe)
+{
+    struct node tmp;
+    if (qs < 0 || qe > n-1 || qs > qe)   {       
+        tmp.minimum = INT_MIN;
+        tmp.minimum = INT_MAX;
+        return tmp;
+    } 
+    return MaxMinUntill(st, 0, n-1, qs, qe, 0);
+}
+
+void constructSTUtil(ll arr[], ll ss, ll se, struct node *st,
+                     ll si)
+{
+    // If there is one element in array, store it in current node of
+    // segment tree and return
+    if (ss == se)
+    {
+        st[si].minimum = arr[ss];
+        st[si].maximum = arr[ss];
+        return ;
+    }
+ 
+    // If there are more than one elements, then recur for left and
+    // right subtrees and store the minimum and maximum of two values
+    // in this node
+    ll mid = getMid(ss, se);
+    constructSTUtil(arr, ss, mid, st, si*2+1);
+    constructSTUtil(arr, mid+1, se, st, si*2+2);
+ 
+    st[si].minimum = min(st[si*2+1].minimum, st[si*2+2].minimum);
+    st[si].maximum = max(st[si*2+1].maximum, st[si*2+2].maximum);
+}
+struct node *constructST(ll arr[], ll n)
+{
+    // Allocate memory for segment tree 
+    // Height of segment tree
+    ll x = (ll)(ceil(log2(n)));
+ 
+    // Maximum size of segment tree
+    ll max_size = 2*(ll)pow(2, x) - 1;
+ 
+    struct node *st = new struct node[max_size];
+ 
+    // Fill the allocated memory st
+    constructSTUtil(arr, 0, n-1, st, 0);
+ 
+    // Return the constructed segment tree
+    return st;
+}
+
+int main()
+{
+	ll t,n,j,i,ctr,flag,mx,mi;
+	cin>>t;
+	
+	while(t--)
+	{
+		ctr=flag =0;
+		cin>>n;
+		ll A[n], B[n];
+		bool alive[n];
+		unordered_map <ll, queue<ll> > mymap;
+		
+		rep(i,0,n)
+		{
+			cin>>A[i];
+		}
+		rep(i,0,n)
+		{
+			cin>>B[i];
+			if(B[i] > A[i])
+				flag = 1;
+			if(B[i]!=A[i])
+				mymap[B[i]].push(i);
+		}
+		if(flag == 1)
+		{
+			cout<<"-1\n";
+			continue;
+		}
+		i=0;
+		while(i<n)
+		{
+			if(A[i]>B[i])
+			{
+				flag = 1;
+				break;
+			}
+			i++;
+		}		
+		if(flag == 0)
+		{
+			cout<<"0\n";
+			continue;
+		}
+		// kaam ka
+		
+		struct node *stA = constructST(A, n),*stB = constructST(B, n);;
+ 
+		int qs = 2;  // Starting index of query range
+		int qe = 6;  // Ending index of query range
+		struct node result=MaxMin(stA, n, qs, qe);
+		
+		//cout<<result.minimum<<" "<<result.maximum<<"\n";
+		 
+		 qs = 1;  // Starting index of query range
+		 qe = 5;  // Ending index of query range
+		  result=MaxMin(stB, n, qs, qe);
+		//cout<<result.minimum<<" "<<result.maximum<<"\n";
+		
+		
+		rep(i,0,n)
+		{
+			if(A[i] ==B[i])
+				alive[i] = false;
+			else
+				alive[i] =true;
+		}
+		rep(i,0,n)
+		{
+			if(alive[i])
+			{
+				//cout<<B[i]<<" -> ";
+				
+				if(mymap[B[i]].size() == 1)
+				{
+					ctr++;
+					continue;
+				}
+				//cout<<B[i]<<" -> ";
+				while(!mymap[B[i]].empty())
+				{
+					qs = mymap[B[i]].front();
+					mymap[B[i]].pop();
+					if(mymap[B[i]].empty())
+						break;
+					qe = mymap[B[i]].front();
+					
+					//cout<<qs<<" "<<qe<<" gives ";
+					
+					mx = MaxMin(stB, n, qs, qe).maximum;										
+					mi = MaxMin(stA, n, qs, qe).minimum;
+					
+					if(mx <= B[i] && mi >= B[i])
+					{
+						alive[qe] = false;
+						//cout<<"false\n";
+					}
+					else
+					{
+						//cout<<"break\n";
+						break;
+						
+					}
+				}
+				/*
+				rep(j,i+1,n)
+				{
+					//cout<<B[j]<<" "<<A[j]<<"\n";
+					if(B[j]>B[i] || A[j]<B[i])
+						break;
+					else if(B[j] == B[i])
+					{
+						alive[j] = false;
+					}
+				}*/
+				ctr++;
+			}
+			//cout<<ctr<<" ";			
+		}
+		cout<<ctr<<"\n";	
+	}	
+	return 0;
+}	
diff --git a/codechef/apr18-div1/goodpref.cpp b/codechef/apr18-div1/goodpref.cpp
new file mode 100644
index 0000000..1960368
--- /dev/null
+++ b/codechef/apr18-div1/goodpref.cpp
@@ -0,0 +1,119 @@
+#include <bits/stdc++.h>
+#include <sstream>
+
+using namespace std;
+
+typedef long long ll;
+typedef vector<int> vi;
+typedef vector<ll> vll;
+typedef pair<int, int> ii;
+typedef vector<ii> vii;
+typedef set<int> si;
+typedef map<string, int> msi;
+
+#define rep(i, a, b) \
+for (int i = int(a); i < int(b); i++) // a to b, and variable i is local!
+#define TRvi(c, it) \
+for (vi::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRvii(c, it) \
+for (vii::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRmsi(c, it) \
+for (msi::iterator it = (c).begin(); it != (c).end(); it++)
+#define INF 2000000000 // 2 billion
+#define mod 1000000007
+
+ll power(ll x, ll y)
+{
+    ll val=1;    
+    x = x%mod;
+    while(y>0)
+    {
+        if(y&1)
+        {
+            val = (val*x)%mod;
+        }
+        y = y>>1;
+        x = (x*x)%mod;
+    }
+    return val;
+}
+
+int main()
+{
+	/*clock_t start,end;
+	start  = clock();*/
+	ll t,n,i,j,a,b,ans,term,d,len;
+	string s;
+ 	cin>>t;
+ 	while(t--)
+    {
+		cin>>s>>n;	
+		
+		len = s.size();
+		ll A[len], B[len];
+		vll indices,indices2;
+		a=b=ans=0;
+		rep(i,0,len)
+		{
+			if(s[i] == 'a')
+				a++;
+			else
+				b++;
+			A[i] = a;
+			B[i] = b;
+			
+			if(A[i]>B[i])
+			{	
+				ans++;
+				indices2.push_back(i);	
+			}
+			else
+				indices.push_back(i);
+		}
+		
+		d = a - b;
+		
+		if(d>0)
+		{
+			ans *= n;
+			rep(i,0,indices.size())
+			{
+				//cout<<indices[i]<<"\n";
+				a = A[indices[i]] - B[indices[i]];
+				term = (-a/d)+1;
+				if(term >n)
+					term  = 0;
+				if(term>0)
+					ans += (n-term);	
+				//cout<<a<<" "<<d<<" "<<term<<"\n";		
+			}
+		}
+		else if(d<0)
+		{
+			ans = 0;
+			rep(i,0,indices2.size())
+			{
+				//cout<<indices2[i]<<"\n";
+				a = A[indices2[i]] - B[indices2[i]];
+				
+				if((-1*a)%d == 0)
+					term = -a/d;
+				else
+					term = -a/d+1;
+				
+				term = min(term,n);				
+				ans += term;	
+				//cout<<a<<" "<<d<<" "<<term<<"\n";		
+			}
+		}
+		else
+			ans *= n;
+		cout<<ans<<"\n";		
+	}
+	
+	
+	/*end = clock();
+	cout<<"\nCPU time used: "<<((double) (end - start)) / CLOCKS_PER_SEC<<" seconds\n";
+	*/
+	return 0;
+}
diff --git a/codechef/apr18-div1/highwayc.cpp b/codechef/apr18-div1/highwayc.cpp
new file mode 100644
index 0000000..32a1005
--- /dev/null
+++ b/codechef/apr18-div1/highwayc.cpp
@@ -0,0 +1,99 @@
+#include <bits/stdc++.h>
+#include <sstream>
+
+using namespace std;
+
+typedef long long ll;
+typedef vector<int> vi;
+typedef vector<ll> vll;
+typedef pair<int, int> ii;
+typedef vector<ii> vii;
+typedef set<int> si;
+typedef map<string, int> msi;
+
+#define rep(i, a, b) \
+for (int i = int(a); i < int(b); i++) // a to b, and variable i is local!
+#define TRvi(c, it) \
+for (vi::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRvii(c, it) \
+for (vii::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRmsi(c, it) \
+for (msi::iterator it = (c).begin(); it != (c).end(); it++)
+#define INF 2000000000 // 2 billion
+#define mod 1000000007
+
+ll power(ll x, ll y)
+{
+    ll val=1;    
+    x = x%mod;
+    while(y>0)
+    {
+        if(y&1)
+        {
+            val = (val*x)%mod;
+        }
+        y = y>>1;
+        x = (x*x)%mod;
+    }
+    return val;
+}
+
+int main()
+{
+	/*clock_t start,end;
+	start  = clock();*/
+	ll t,i,j;
+	long double n,s,y,time;
+ 	cin>>t;
+ 	while(t--)
+    {
+		cin>>n>>s>>y;
+		vector<long double> V(n), D(n), P(n),C(n), I(n);
+		rep(i,0,n)
+			cin>>V[i];
+		rep(i,0,n)
+			cin>>D[i];
+		rep(i,0,n)
+		{			
+			cin>>P[i];
+			I[i] = P[i];
+		}
+		rep(i,0,n)
+			cin>>C[i];	
+				
+		time = 0.0;
+		rep(i,0,n)
+		{
+			if(D[i] == 1)
+			{
+				P[i] = I[i] + (V[i]*time); 				
+			}
+			else
+			{
+				P[i] = I[i] - (V[i]*time); 
+			}			
+			if(P[i] >= 0 && D[i] == 0) 
+			{
+				if( P[i]/V[i] <= y/s || (P[i] - V[i]*y/s) <= 0.000001)
+					time += (P[i]+C[i])/V[i];				
+			}
+			else if((P[i] < 0 && D[i] == 1))
+			{
+				if((-1.0*P[i])/V[i] <= y/s || abs(P[i] + V[i]*y/s) <= 0.000001)
+					time += (abs(P[i])+C[i])/V[i];
+			}
+			else if(P[i] >= 0 && D[i] == 1 && P[i] < C[i])
+			{
+				time += abs(C[i] - P[i])/V[i];
+			}
+			else if(P[i] < 0 && D[i] == 0 && -1*P[i] < C[i])
+			{
+				time += (C[i] - abs(P[i]))/V[i];
+			}			
+			time +=y/s;
+		}
+		cout<<setprecision(20);
+		cout<<time<<"\n";
+	}
+	return 0;
+}	
diff --git a/codechef/apr18-div1/jadugar.cpp b/codechef/apr18-div1/jadugar.cpp
new file mode 100644
index 0000000..f3b6749
--- /dev/null
+++ b/codechef/apr18-div1/jadugar.cpp
@@ -0,0 +1,108 @@
+#include <bits/stdc++.h>
+#include <sstream>
+ 
+using namespace std;
+ 
+typedef long long ll;
+typedef vector<int> vi;
+typedef vector<ll> vll;
+typedef pair<int, int> ii;
+typedef vector<ii> vii;
+typedef set<int> si;
+typedef map<string, int> msi;
+ 
+#define rep(i, a, b) \
+for (int i = int(a); i < int(b); i++) // a to b, and variable i is local!
+#define TRvi(c, it) \
+for (vi::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRvii(c, it) \
+for (vii::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRmsi(c, it) \
+for (msi::iterator it = (c).begin(); it != (c).end(); it++)
+#define INF 2000000000 // 2 billion
+#define mod 1000000007
+ 
+ll power(ll x, ll y)
+{
+    ll val=1;    
+    x = x%mod;
+    while(y>0)
+    {
+        if(y&1)
+        {
+            val = (val*x)%mod;
+        }
+        y = y>>1;
+        x = (x*x)%mod;
+    }
+    return val;
+}
+ 
+int main()
+{
+	/*clock_t start,end;
+	start  = clock();*/
+	ll t,d,n,i,j,K,A,B,q,l,r,ans,a,b,Asq, c;
+ 
+	cin>>n>>K>>A>>B;
+	
+	vll dp(n+1);//,sum(n+1);
+	//ll s=0;
+	dp[1] = K;
+	//sum[1] =(power(K,2))%mod;
+	dp[2] = (((A%mod)*(K%mod))%mod + ((B%mod)*power(K,2))%mod)%mod;
+	//cout<<sum[0]<<" ";
+	c = (A+(((2*K%mod)*(B%mod))%mod))%mod;
+	Asq = power(A,2);
+	//cout<<dp[1]<<" "<<dp[2]<<" ";
+	
+	rep(i,3,n+1)
+	{
+		//dp[i] = (((A+(2*((K%mod)*(B%mod))%mod)%mod)%mod)*((2*i-3)*(dp[i-1]))%mod)%mod;
+		
+		a = ((((2*i-3)*(dp[i-1]%mod))%mod)*(c)%mod);
+		b = (((Asq*(i-3))%mod)*dp[i-2])%mod;
+			
+		if(a-b >=0)
+			dp[i] = a-b;
+		else
+			dp[i] = a-b+mod;
+		
+		dp[i] = (power(i,mod-2)*dp[i])%mod;
+	
+		//cout<<dp[i]<<" ";
+		//dp[i] = ((((4*i-2)*(dp[i-1]%mod))%mod)*(((K%mod)*(B%mod))%mod))%mod;
+		//dp[i] = (power(i+1,mod-2)*dp[i])%mod;
+		//sum[i] = (sum[i-1] + power(dp[i],2)%mod)%mod;
+		//cout<<sum[i]<<" ";
+	}
+	
+	cout<<dp[n];
+	/*
+	cin>>q; 
+	while(q--)
+	{
+		cin>>l>>r;
+		ans =0;
+		
+		if(l == 1)
+		{
+			ans = sum[r-1];	
+		}
+		else
+		{
+			ans = (sum[r-1] - sum[l-2])%mod;
+		}
+		if(ans <0)
+			ans+=mod;
+		cout<<ans%mod<<"\n";
+	}
+	
+	*/
+	/*end = clock();	
+	cout<<"\nCPU time used: "<<((double) (end - start)) / CLOCKS_PER_SEC<<" seconds\n";
+	*/
+	
+	
+	return 0;
+}
diff --git a/codechef/apr18-div1/jadugar2.cpp b/codechef/apr18-div1/jadugar2.cpp
new file mode 100644
index 0000000..3e98abb
--- /dev/null
+++ b/codechef/apr18-div1/jadugar2.cpp
@@ -0,0 +1,110 @@
+#include <bits/stdc++.h>
+#include <sstream>
+ 
+using namespace std;
+ 
+typedef long long ll;
+typedef vector<int> vi;
+typedef vector<ll> vll;
+typedef pair<int, int> ii;
+typedef vector<ii> vii;
+typedef set<int> si;
+typedef map<string, int> msi;
+ 
+#define rep(i, a, b) \
+for (int i = int(a); i < int(b); i++) // a to b, and variable i is local!
+#define TRvi(c, it) \
+for (vi::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRvii(c, it) \
+for (vii::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRmsi(c, it) \
+for (msi::iterator it = (c).begin(); it != (c).end(); it++)
+#define INF 2000000000 // 2 billion
+#define mod 1000000007
+ 
+ll power(ll x, ll y)
+{
+    ll val=1;    
+    x = x%mod;
+    while(y>0)
+    {
+        if(y&1)
+        {
+            val = (val*x)%mod;
+        }
+        y = y>>1;
+        x = (x*x)%mod;
+    }
+    return val;
+}
+ 
+int main()
+{
+	/*clock_t start,end;
+	start  = clock();*/
+	ll t,d,n,i,j,K,A,B,q,l,r,ans,a,b,Asq, c;
+ 
+	cin>>n>>K>>A>>B;
+	
+	vll dp(n+1),sum(n+1);
+	//ll s=0;
+	dp[1] = K;
+	sum[1] =(power(K,2))%mod;
+	dp[2] = (((A%mod)*(K%mod))%mod + ((B%mod)*power(K,2))%mod)%mod;
+	//cout<<sum[0]<<" ";
+	c = (A+(((2*K%mod)*(B%mod))%mod))%mod;
+	Asq = power(A,2);
+	//cout<<dp[1]<<" "<<dp[2]<<" ";
+	
+	sum[2] = (sum[1]+(power(dp[2],2))%mod)%mod;
+	//cout<<sum[1]<<" "<<sum[2]<<" ";
+	rep(i,3,n+1)
+	{
+		//dp[i] = (((A+(2*((K%mod)*(B%mod))%mod)%mod)%mod)*((2*i-3)*(dp[i-1]))%mod)%mod;
+		
+		a = ((((2*i-3)*(dp[i-1]%mod))%mod)*(c)%mod);
+		b = (((Asq*(i-3))%mod)*dp[i-2])%mod;
+			
+		if(a-b >=0)
+			dp[i] = a-b;
+		else
+			dp[i] = a-b+mod;
+		
+		dp[i] = (power(i,mod-2)*dp[i])%mod;
+	
+		//cout<<dp[i]<<" ";
+		//dp[i] = ((((4*i-2)*(dp[i-1]%mod))%mod)*(((K%mod)*(B%mod))%mod))%mod;
+		//dp[i] = (power(i+1,mod-2)*dp[i])%mod;
+		sum[i] = (sum[i-1] + power(dp[i],2)%mod)%mod;
+		//cout<<sum[i]<<" ";
+	}
+	
+	//cout<<dp[n];
+	
+	cin>>q; 
+	while(q--)
+	{
+		cin>>l>>r;
+		ans =0;
+		
+		if(l == 1)
+		{
+			ans = sum[r];	
+		}
+		else
+		{
+			ans = (sum[r] - sum[l-1])%mod;
+		}
+		if(ans <0)
+			ans+=mod;
+		cout<<ans%mod<<"\n";
+	}
+	
+	
+	/*end = clock();	
+	cout<<"\nCPU time used: "<<((double) (end - start)) / CLOCKS_PER_SEC<<" seconds\n";
+	*/
+	
+	
+	return 0;
+}
diff --git a/codechef/apr18-div1/vaimin.cpp b/codechef/apr18-div1/vaimin.cpp
new file mode 100644
index 0000000..acdbcdb
--- /dev/null
+++ b/codechef/apr18-div1/vaimin.cpp
@@ -0,0 +1,99 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+typedef long long ll;
+typedef vector<int> vi;
+typedef vector<ll> vll;
+typedef pair<int, int> ii;
+typedef vector<ii> vii;
+typedef set<int> si;
+typedef map<string, int> msi;
+
+#define rep(i, a, b) \
+for (int i = int(a); i < int(b); i++) // a to b, and variable i is local!
+#define TRvi(c, it) \
+for (vi::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRvii(c, it) \
+for (vii::iterator it = (c).begin(); it != (c).end(); it++)
+#define TRmsi(c, it) \
+for (msi::iterator it = (c).begin(); it != (c).end(); it++)
+#define INF 2000000000 // 2 billion
+#define mod 1000000007
+
+int main() {
+    ll t,n,p,q,c,i,j,k,m,g,b,flag=0;
+    set<pair<ll, ll> > myset;
+   	cin>>p>>q>>c>>m;
+    //p = 15; q = 15;m=0;c=0;
+    rep(i,0,m)
+	{
+	    cin>>g>>b;
+	    if(g<c && b==0)
+	    {
+	    	flag=1;
+	    }
+	    myset.insert(make_pair(g,b));
+	} 
+	
+    if(p-c < q || (p == 0 && q == 0 && c==0) || flag == 1)
+    {
+    	cout<<"0\n";
+    	return 0;
+    }
+    
+    ll A[p-c+1][q+1];
+        
+    rep(i,0,p-c+1)
+    {
+        rep(j,i+1,q+1)
+        {
+            A[i][j] = 0;
+        }
+    }
+      
+    flag = 0;
+	rep(i,0,p-c+1)
+	{
+		if(flag == 1)
+		{
+			A[i][0] = 0;
+		}
+		else
+		{
+			if(myset.find(make_pair(i+c,0))==myset.end())
+		    {
+		        A[i][0] = 1;
+		    }
+		    else
+		    {		    	
+		    	flag = 1;
+				A[i][0] = 0;
+			}
+	    }
+	}	
+	
+    rep(i,1,p-c+1)
+    {
+        rep(j,1,min(ll(i+1),q+1))
+        {
+            if(myset.find(make_pair(i+c,j))==myset.end())
+            {
+                A[i][j] = (A[i-1][j]+A[i][j-1])%mod;
+            }
+            else
+            	 A[i][j] = 0;
+        }
+    }
+   /* 
+    rep(i,0,p-c+1)
+    {
+        rep(j,0,q+1)
+        {
+            cout<<A[i][j]<<" ";
+        }
+        cout<<"\n";
+    }
+  */
+ 	cout<<A[p-c][q]<<"\n";
+	return 0;
+}