Shortest Common Supersequence

#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
#include <complex>
#include <queue>
#include <set>
#include <unordered_set>
#include <list>
#include <chrono>
#include <random>
#include <iostream>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <map>
#include <unordered_map>
#include <stack>
#include <iomanip>
#include <fstream>

using namespace std;

string SCS(string ans, string &s1, string &s2, int i, int j){
    if(i<0 && j<0) return ans;

    if(i<0){
        while(j>=0){
            ans.push_back(s2[j]); j--;
        }
        reverse(ans.begin(),ans.end());
        return ans;
    }

    if(j<0){
        while(i>=0){
            ans.push_back(s1[i]); i--;
        }
        reverse(ans.begin(),ans.end());
        return ans;
    }

    if(s1[i] == s2[j]){
        ans = SCS(ans,s1,s2,i-1,j-1);
        ans.push_back(s1[i]);
    }
    else{
        string temp1 = SCS(ans,s1,s2,i-1,j);
        string temp2 = SCS(ans,s1,s2,i,j-1);
        if(temp1.size() < temp2.size()){
            ans = temp1; ans.push_back(s1[i]);
        }
        else{
            ans = temp2; ans.push_back(s2[j]);
        }
    }

    return ans;
}

int main(){

    string s1, s2;
    cin>>s1>>s2;
    string ans = "";
    int n1 = s1.size();
    int n2 = s2.size();
    ans = SCS(ans,s1,s2,n1-1,n2-1);
    cout<<ans;
 return 0;
}