#include <iostream>
using namespace std;
string a,b; 
int main()
{
	cin>>a>>b;
	if(a.size()>b.size())//先判断字符串长度 
	{
		if(a.find(b)!=-1)//寻找有没有重合 
		{
			cout<<b<<" is substring of "<<a;
		}
		else
		{
			cout<<"No substring";
		}
	}
	else
	{
		if(b.find(a)!=-1)
		{
			cout<<a<<" is substring of "<<b;
		}
		else
		{
			cout<<"No substring";
		}
	}
	
	
	
	
	
	
	
	
	
	return 0;
}