#include<bits/stdc++.h>
using namespace std;
int main(){
string s1, s2;
cin >> s1 >> s2;
if(s1.find(s2) != -1)
cout << s2 << " is substring of " << s1;
else if(s2.find(s1) != -1)
cout << s1 << " is substring of " << s2;
else cout << "No substring";
return 0;
}
