ModAdd

#include <bits/stdc++.h>

#define _ ios_base::sync_with_stdio(0);cin.tie();
#define ll long long
#define vi vector<int>
#define pb push_back
#define pii pair<int, int>
#define vpii vector<pii>

using namespace std;

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);

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

    if(a=="0" && b=="0") {
        cout << "0" << '\n';
        return 0;
    }

    if(a == "0") {
        cout << b << '\n';
        return 0;
    }

    if(b == "0") {
        cout << a << '\n';
        return 0;
    }

    int len = min(a.length(), b.length());
    int diff = 0;
    if(a.length() > b.length()) {
        diff = a.length() - b.length();
        cout << a.substr(0, diff);
        a.erase(0, diff);
    }
    if(b.length() > a.length()) {
        diff = b.length() - a.length();
        cout << b.substr(0, diff);
        b.erase(0, diff);
    }

    bool leading = true;

    for(int i=0;i<len;i++) {
        int sum = 0;
        sum = (a[i]-48) + (b[i]-48);
        if(leading == true && sum % 10 == 0) {
            continue;
        }
        leading = false;
        cout << sum % 10;
    }

    if(leading)
        cout << '0';

    cout << '\n';

	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