#include <bits/stdc++.h>
using namespace std;
int fn(int x) {
  int i = 1;
  while (i * (i + 1) / 2 < x) {
    i++;
  }
  if (i * (i + 1) / 2 > x) {
    i--;
  }
  return i;
}
int main() {
  int k;
  cin >> k;
  char c = 'a';
  string ans = "";
  int fl = k;
  while (k > 0) {
    int x = fn(k);
    for (int i = 0; i <= x; i++) ans += c;
    c++;
    k -= x * (x + 1) / 2;
  }
  if (fl)
    cout << ans << endl;
  else
    cout << "a" << endl;
}
