#include <bits/stdc++.h>
using namespace std;
int f(int n) {
  double b = ((sqrt(1.0 + 8.0 * n)) - 1) / 2.0;
  int c = (int)b;
  return c + 1;
}
int koita(int n) { return (n * (n - 1)) / 2; }
int main() {
  int k;
  scanf("%d", &k);
  string s = "";
  int ct = 0;
  while (1) {
    int a = f(k);
    for (int i = 1; i <= a; i++) s += ('a' + ct);
    int aa = koita(a);
    k -= aa;
    if (!k) break;
    ct++;
  }
  cout << s;
  return (0);
}
