#include <iostream>
#include <vector>
#include<string>
#include<algorithm>
using namespace std;

int reverse(int n){
	int sum = 0;
	int t = 1;
	while(n){
		int remain = n%10;
		sum = sum*t + remain;
		n/=10;
		t*=10;
	}
	return sum;
}

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