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

int Reverse(int x){
    int num=0;
    while(x>0){
        num+=num*10+x%10;
        x/=10;
    }
    return num;
}

int main() {
    int a,b;
    while(scanf("%d%d",&a,&b)!=EOF){
        if(Reverse(a)+Reverse(b)==Reverse(a+b)){
            printf("%d",a+b);
        }else {
            printf("NO");
        }
    }
    return 0;
}
// 64 位输出请用 printf("%lld")