#include <cstdlib>
#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <string>
using namespace std;

int main() {
    string a, b;
    while (cin >> a >> b) {
        int num1=atoi(a.c_str())+atoi(b.c_str());
        reverse(a.begin(),a.end());
        reverse(b.begin(),b.end());
        int num2=atoi(a.c_str())+atoi(b.c_str());
        string str1=to_string(num1);
        string str2=to_string(num2);
        reverse(str2.begin(),str2.end());
        if(str1==str2)
        {
            cout<<num1<<endl;
        }
        else {
            cout<<"NO"<<endl;
        }      
    }
    return 0;
}