#include<bits/stdc++.h>
using namespace  std;
string s1,s2; 
int  main( ) 
{
    cin>>s1>>s2;
    int a=s2.find(s1);
    int b=s1.find(s2);
    if (a!=-1)
        cout<<s1<<" is substring of "<<s2;
    else if (b!=-1)
        cout<<s2<<" is substring of "<<s1;
    else
        cout<<"No substring";
    return 0;   
}