include<iostream>

include<string>

include<stdlib.h>

include<algorithm>

using namespace std;

int main()
{
int a,b;
cin>>a>>b;

int sum1=a+b;
string sa;
string sb;
sa = to_string(a);
sb = to_string(b);
string  ssum1 = to_string(sum1);
reverse(sa.begin(),sa.end());
reverse(sb.begin(),sb.end());
reverse(ssum1.begin(),ssum1.end());
int aa= atoi(sa.c_str());
int bb= atoi(sb.c_str());
int sum2=aa+bb;
string ssum2=to_string(sum2);
if(ssum1==ssum2) cout<<sum1;
else cout<<"NO"<<endl;

return 0;

}