#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  string ans;
  string abc;
  abc = "abcdefghijklmnopqrstuvwxyz";
  cin >> n;
  int j = 0;
  if (n == 0) ans = "a";
  while (n) {
    int d = floor(sqrt(1 + 8 * n));
    int s = floor((-1 + d) / 2.0);
    for (int i = 0; i <= s; i++) ans.append(abc, j, 1);
    n = n - ((s * (s + 1)) / 2);
    j++;
  }
  cout << ans;
  return 0;
}
