#include <bits/stdc++.h>
using namespace std;
void fast() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
}
int main() {
  int k;
  cin >> k;
  int n = 1;
  int x = 0, q = 0;
  string a = "";
  while (1) {
    n = 1;
    while (1) {
      x = (n * (n + 1)) / 2;
      if (x > k) {
        n--;
        break;
      }
      n++;
    }
    x = (n * (n + 1)) / 2;
    k = k - (x);
    for (long long i = 0; i < n + 1; i++) a += ('a' + q);
    q++;
    if (k == 0) break;
  }
  cout << a;
  return 0;
}
