#include <iostream>
using namespace std;

int reverse(int x){
    int res=0;
    while(x){
        res=res*10+x%10;
        x/=10;
    }
    return res;
}

int main() {
    int a,b;
    while(cin>>a>>b){
        int sum1=reverse(a)+reverse(b);
        int sum2=reverse(a+b);
        if(sum1==sum2) cout<<a+b<<endl;
        else cout<<"NO"<<endl;
    }
    return 0;
}