#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  int k, x = 0;
  char c = 'a';
  cin >> k;
  while (k) {
    x = 0;
    s += c;
    for (int i = 1; i <= k; i++) {
      if (x + i > k) break;
      x += i;
      s += c;
    }
    k -= x;
    c++;
  }
  if (s.size() == 0) s = 'a';
  cout << s << "\n";
}
