ModAdd

#include <iostream>
#include <cstring>
using namespace std;

int main(){
	ios::sync_with_stdio(0);
	string n,m;
	cin>>n;
	cin>>m;
	
	long long lengthn = n.length(); 
	long long lengthm = m.length(); 
	long long max = lengthn > lengthm ? lengthn : lengthm;
	bool trailZero = true;
	long long nc=0, mc=0;
	for (long long i = 0; i <= max-1; i++) {
		int j,k;
		if(lengthn<lengthm){
			lengthn++;
			j = 0;
		} else{
			j = (int) n[nc++]-48;
		}
		if(lengthm<lengthn){
			lengthm++;
			k= 0;
		} else{
			k = (int) m[mc++]-48;

		}
		int l = (j + k) % 10;
		if (i == max-1 && trailZero && l==0){
			cout<<"0";
		}
		if(l==0 && trailZero){
			continue;
		}
		trailZero = false;
		cout<<l;
	}
	
	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