#include<bits/stdc++.h>
using namespace std;
#ifdef LOCAL_DEBUG
  #include "LOCAL_DEBUG.hpp"
#endif
#define int long long

signed main(){

  int n; cin >> n;
  int k = (n + 26) / 26;
  char c = 'A' + n % 26;
  string ans;
  for(int i = 0; i < k; i++){
    ans += c;
  }
  cout << ans << endl;

  return 0;
}