#include<iostream>
#include<string>
#include<algorithm>
using namespace std;

int n;
string s1,s2;
int main(){
	cin>>s1>>s2;
	int t=s1.find(s2);
	int x=s2.find(s1);
	if(t==-1)
	{
		if(x==-1)
		{
			cout<<"No substring"; 
			return 0;
		}
		else
		{
			cout<<s1<<" is substring of "<<s2; 
			return 0;
		}
	}
	else
	{
		if(x==-1)
		{
			cout<<s2<<" is substring of "<<s1;
				return 0; 	
		}
	}
	return 0;
}