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