Envío 5500

Código

#include <bits/stdc++.h>
#define REP(i,n) for(int i=0; i<n;i++)
#define pb push_back
#define ff first
#define ss second
#define ii pair<int,int>
#define vi vector<int>
#define vii vector<ii>
#define lli long long int
#define fast_io ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
using namespace std;
ostream& operator<<(ostream& os, const vector<int> &v){
    for(auto const &i: v){
        os<<i<<" ";
    }
    os<<endl;
    return os;
}
const lli mod=(1e9)+7;
const int N = 1e4+1;
int main(){
    fast_io;
    string a;cin>>a;
    string b;cin>>b;
    if(a.size()<b.size())swap(a,b); //el mayor en a
    int dif = abs((int)a.size()-(int)b.size());
    string tmp = "";
    REP(i,dif)tmp+='0';
    b = tmp+=b;
    //cout<<a<<endl;
    //cout<<b<<endl;
    int llevo = 0;
    string ans = "";
    for(int i = b.size()-1; i>=0; i--){
        int aa = a[i]-'0';
        int bb = b[i]-'0';
        char res = ((aa+bb+llevo)%10)+'0';
        ans+=res;
        if(aa+bb+llevo>=10)llevo = 1;
        else llevo = 0;
    }
    if(llevo)ans+='1';
    for(int i=ans.size() - 1;i>=0;i--){
        cout<<ans[i];
    }
    cout<<endl;
    return 0;
}