#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, m, l, i, j, flag;
  cin >> n;
  m = 26;
  l = 1;
  while (m < n) {
    m *= 26;
    l++;
  }
  m /= 26;
  char t[l];
  for (i = 0; i < l; i++) {
    j = 0;
    flag = 1;
    while (flag == 1) {
      if (n - m >= 0) {
        j++;
        n -= m;
      } else
        flag = 0;
    }
    t[i] = 'a' + j - 1;
    m /= 26;
  }
  cout << t << endl;
}
