#include <iostream>
#include <cstdio>
#include <string>

using namespace std;

int main()
{
	string s1, s2;
	getline(cin, s1);
	getline(cin, 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;
}