#include <bits/stdc++.h> using namespace std ; const int N = 30 ; int n ; string s[N] ; int main() { cin >> n ; s[1] = "A" ; for(int i = 2 ; i <= n ; i++ ) s[i] = s[i - 1] + string('A' + i - 1) + s[i - 1]; cout << s[n] << endl ; return 0 ; }