#include <bits/stdc++.h>
using namespace std;
int main() {
  int k;
  cin >> k;
  putchar('z');
  for (int i = 0; k > 0 && i < 25; i++) {
    int r = 0;
    while ((r * r - r) / 2 <= k) r++;
    r--;
    k -= (r * r - r) / 2;
    while (r--) putchar('a' + i);
  }
  putchar('\n');
  return 0;
}
