//C++版代码
#include <iostream>
using namespace std;
int reverseNum(int x) {
int ret = 0;
while (x) {
ret = ret * 10 + x % 10;
x /= 10;
}
return ret;
}
int main() {
int a, b;
while (cin >> a >> b) {
if (reverseNum(a) + reverseNum(b) == reverseNum(a + b)) cout << a + b << endl;
else cout << "NO" << endl;
}
return 0;
}
//Java版代码
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
while (sc.hasNextInt()) {
int a = sc.nextInt();
int b = sc.nextInt();
if (reverseNum(a) + reverseNum(b) == reverseNum(a + b)) System.out.println(a + b);
else System.out.println("NO");
}
}
private static int reverseNum(int x) {
return Integer.parseInt(new StringBuilder(Integer.toString(x)).reverse().toString());
}
}
#Python版代码
while True:
try:
a, b = input().split()
print(int(a) + int(b) if int(a[::-1]) + int(b[::-1]) == int(str(int(a) + int(b))[::-1]) else 'NO')
except:
break