#include<iostream>
#include<string>
#include<algorithm>
using namespace std;

int main(){
    int a, b;
    int r_of_sum, sum_of_r;
    string sa, sb, ssum;
    while(cin >> a){
        cin >> b;
        r_of_sum = a + b;
        string tmp = to_string(r_of_sum);
        reverse(tmp.begin(), tmp.end());
        r_of_sum = atoi(tmp.c_str());

        sa = to_string(a);
        sb = to_string(b);
        reverse(sa.begin(), sa.end());
        reverse(sb.begin(), sb.end());
        sum_of_r = atoi(sa.c_str()) + atoi(sb.c_str());
        if(r_of_sum == sum_of_r){
            cout << a + b << endl;
        } else {
            cout << "NO" << endl;
        }
    }
    return 0;
}