1177 A. Digits Sequence (Easy Edition).cpp

#include<bits/stdc++.h>
#define ll              long long
#define ull             unsigned long long
#define pb              push_back
#define fastread()      (ios_base:: sync_with_stdio(false),cin.tie(NULL));
using namespace std;
int main()
{
    fastread();

    //freopen("input.txt","r", stdin);

    ll n;
    cin>>n;

    vector<int>v;
    stack<int>st;

    for(ll i=1; i<=5000; i++){
        if(i < 10){
            v.pb(i);
        }
        else{
            int a = i,d;
            while(a >= 10){
                d = a % 10;
                a = a / 10;
                st.push(d);
            }
            st.push(a);
            while(!st.empty()){
                d = st.top();
                st.pop();
                v.pb(d);
            }
        }
    }
//    for(ll i=0; i<n; i++){
//        cout<<v[i]<<" ";
//    }
//    cout<<endl;
    cout<<v[n-1]<<endl;
    return 0;
}