#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; }