#include <bits/stdc++.h>
using namespace std;
string s1;
string s2;
int main(){
	cin>>s1>>s2;
	int sum;
	for(int i=0;i<=s1.size()-(s2.size()-1);i++){
		if(s1[i]==s2[0]){
			sum=0;
			for(int a=1;a<=s2.size()-1;a++)
				if(s1[i+a]==s2[a])
					sum++;
		}
		if(sum==s2.size()-1){
			if(s1.size()>s2.size())
				cout<<s2<<" is substring of "<<s1<<endl;
			else
				cout<<s1<<" is substring of "<<s2<<endl;
			return 0;
		}
	}
	cout<<"No substring"<<endl;
	return 0;
}