ModAdd

using namespace std;
#include <bits/stdc++.h>

#define sz(x) ((int)x.size())
#define sqr(x) ((x)*(x))
#define pb push_back
#define clr clear()
#define inf (1<<30)
#define eps 1e-9
typedef long long i64;
typedef unsigned long long ui64;
#include <math.h>



int main() {
    ios_base::sync_with_stdio(0);

    string a, b;
    cin >> a >> b;

    int nb_digit_a = a.length();
    int nb_digit_b = b.length();

    vector<int> va;
    for(int i = nb_digit_a - 1 ; i >= 0 ; i--){
        va.push_back(a[i] - '0');
    }

    vector<int> vb;
    for(int i = nb_digit_b - 1 ; i >= 0 ; i--){
        vb.push_back(b[i] - '0');
    }

    int max_digit = max(nb_digit_a, nb_digit_b);

    vector<int> res;
    for(int i = 0; i < max_digit; i++){
        if(i < nb_digit_a && i < nb_digit_b){
            res.push_back((va[i] + vb[i]) % 10);
        }else if(i >= nb_digit_b && i < nb_digit_a){
            res.push_back((va[i]) % 10);
        }else {
            res.push_back((vb[i]) % 10);
        }
    }

    reverse(res.begin(), res.end());

    bool leading = true;
    bool no_ouput = true;
    for(auto it : res){

        if(it != 0 && leading){
            leading = false;
        }

        if(it != 0 || !leading){
            no_ouput = false;
            cout << it;
        }
    }

    if(no_ouput){
        cout << 0;
    }
    cout << endl;

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED