#include <bits/stdc++.h>
using namespace std;
const int N = 1;
int C(int a) { return a * (a - 1) / 2; }
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int k, cnt = 0;
  string ans = "";
  cin >> k;
  if (k == 0) return cout << 'a' << endl, 0;
  while (k) {
    int i;
    for (i = 2; i <= 1000; i++)
      if (C(i) > k) break;
    i--;
    k -= C(i);
    while (i--) ans += 'a' + cnt;
    cnt++;
  }
  cout << ans << endl;
  return 0;
}
