#include <bits/stdc++.h>
using namespace std;
void fast() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
}
char to_char(int n) {
  if (n == 0) return 'z';
  char res = n + 96;
  return char(res);
}
void solve() {
  long long int n;
  cin >> n;
  string s;
  while (n > 0) {
    char temp = to_char(n % 26);
    s = temp + s;
    if (n % 26 == 0)
      n = n / 26 - 1;
    else
      n = n / 26;
  }
  cout << s << endl;
}
int main() {
  fast();
  solve();
  return 0;
}
