#include<bits/stdc++.h>
using namespace std;
string a,b,temp; 
int cmp(string a,string b){
	int len0 = a.size();
	int len1 = b.size();
	if(len0>len1){
		return 1;
	}else{
		return 0;
	}
}
int main(){
	cin>>a>>b;
	if(cmp(a,b)){
		temp = a;
		a =b;
		b = temp;
	}int len = b.size();
		for(int i = 0; i<len;i++){
			if(b[i] == a[0]){
				int  flag = true;
				for(int j = 0;j<a.size();j++){
					if(b[i+j] == a[j]){
						
					}else {
						flag = false;
						break;
					}
				}
				if(flag){
					cout<<a<<" is substring of "<<b;
					return 0;
				}
			}
		}
	cout<<"No substring";
				
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
string a,b,c;
int main(){
    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";
	}
    return 0;
}