#include <bits/stdc++.h>
using namespace std;
long long n;
int main() {
  cin >> n;
  if (n == 0) {
    cout << "ab";
    return 0;
  }
  long long alpha = 0;
  while (n != 0) {
    long long rep = (long long)sqrt(n * 2);
    long long cal = (rep * (rep + 1)) / 2;
    if (n < cal) rep--;
    cal = (rep * (rep + 1)) / 2;
    for (long long i = 0; i < rep + 1; i++) {
      cout << char('a' + alpha);
    }
    alpha++;
    n -= cal;
  }
  return 0;
}
