#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;
}