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