#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
const int N = 1e6 + 10;
int t, n, m, k, l, r, op, x, y, a, b, c;
int rev(int x) {
    int ans = 0;
    while (x) {
        ans = ans*10 +x % 10;
        x /= 10;
    }
    return ans;
}
void solve() {
    while (cin >> a >> b) {
        c = a + b;
        a = rev(a);
        b = rev(b);
        if(a+b==rev(c)){
            cout<<c;
        }else{
            cout<<"NO";
        }
        cout<<"\n";
    }
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    solve();
    return 0;
}