#include <bits/stdc++.h>
using namespace std;
int main(){
#define ll long long
string a;
string b;
cin>>a>>b;
ll sizea = a.size();
ll sizeb = b.size();
int kg=0;
int i=0;
int j=0;
for(i=0;i<sizea;i++){
    string temp=a.substr(i,3);
    if(temp==b){
        cout<<b<<" is substring of "<<a;
        break;
    }
 
    
    
    }
   if(i==sizea) kg++;
for(j=0;j<sizeb;j++){
    string temp=b.substr(j,3);
    
    
    if(temp==a){
        cout<<a<<" is substring of "<<b;
        break;
    }
 
    }
    if(j==sizeb) kg++;
    if(kg>=2){
        cout<<"No substring";
    }

return 0;
}