#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int, int>;
int main() {
  ll n;
  cin >> n;
  int i = 0;
  string s = "";
  while (n > 0) {
    s.insert(s.begin(), (char)((n - 1) % 26 + 97));
    n = (n - 1) / 26;
  }
  cout << s << endl;
  return 0;
}
