#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  cin >> n;
  long long a[1000], k;
  string s = "";
  for (k = 0, a[0] = 0; a[k] <= n; k++, a[k] = k * (k + 1) / 2)
    ;
  for (char c = 'a'; n > 0; c++) {
    long long m = 0;
    for (m = k - 1; a[m] > n; m--)
      ;
    n -= a[m];
    for (int i = 0; i <= m; i++) {
      s = s + c;
    }
  }
  s += "z";
  cout << s;
  return 0;
}
