#include <iostream>
using namespace std;
string s, b;

int main() {
	cin >> b >> s;
	if (s.length()  > b.length() ) {
		swap(s, b);
	}
	for (int i = 0; i <= s.length(); i++) {
		int l = 0;
		for (int j = 0; i < b.length(); j++) {
			if (s[i + j] == b[j])
				l++;
			else
				break;
		}
		if (l == s.size()) {
			cout << b << " is substring of " << s << endl;
			return 0;
		}
	}
	cout << "No substring";

	return 0;
}