#include<bits/stdc++.h>
using namespace std;
int diandao(int c){
if(c/100000!=0)
return c%10*100000+c%100/10*10000+c/100000+c%10000/1000*100+c%1000/100*1000+c%10000/1000*10;
else if(c/10000!=0)
return c%10*10000+c%100/10*1000+c/10000+c%10000/1000*10+c%1000/100*100;
else if(c/1000!=0)
return c/1000+c%1000/100*10+c%100/10*100+c%10*1000;
else if(c/100!=0)
return c/100+c%100/10*10+c%10*100;
else if(c/10!=0)
return c/10+c%10*10;
else return c;
}
int main() {
int a=0;
while(cin>>a)
{
int b=0;
cin>>b;
int c=a+b;
if(diandao(a)+diandao(b)==diandao(c))
cout<<c<<endl;
else cout<<"NO"<<endl;
}
return 0;
}