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