#include <bits/stdc++.h>
using namespace std;

int main()
{
    string s1;
    string s2;

    getline(cin, s1);
    cin.ignore();
    getline(cin, s2);

    int i = 0, j = 0;
    while (i < s2.size() && j < s1.size())
    {
        if (s1[j] == s2[i])
        {
            j++;
            i++;
        }
        else
        {
            i = i - j + 1;
            j = 0;
        }
    }
    if ( j==s1.size())
    {
        cout << s1 << " is substring of " << s2;
    }
    else
    {
        cout << "No substring";
    }
    return 0;
}