#include<bits/stdc++.h>
using namespace std;
char a[1005],b[1005];
int main(){
	cin.getline(a,1005);
	cin.getline(b,1005);
	if(strstr(a,b)!=NULL) cout<<b<<" is substring of "<<a;
	else if(strstr(b,a)!=NULL) cout<<a<<" is substring of "<<b;
	else cout<<"No substring";
	return 0;
}