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