#include <bits/stdc++.h>
using namespace std;
int main() {
int a, b;
while (cin >> a >> b) { // 注意 while 处理多个 case
int a1 = 0, b1 = 0, sum = a + b;
while (a) {
a1 = a1 * 10 + a % 10;
a /= 10;
}
while (b) {
b1 = b1 * 10 + b % 10;
b /= 10;
}
a1 += b1;
b1 = 0;
while (a1) {
b1 = b1 * 10 + a1 % 10;
a1 /= 10;
}
if (b1 == sum) {
cout << sum << endl;
} else {
cout << "NO" << endl;
}
}
}
// 64 位输出请用 printf("%lld")

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