#include <bits/stdc++.h>
using namespace std;
int k;
string ans;
int sum(int t) {
  int r = sqrt(2 * t);
  while (r * (r + 1) / 2 > t) r--;
  return r;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  char curL = 'a';
  cin >> k;
  if (!k) return cout << 'a' << endl, 0;
  while (k) {
    int cur = sum(k);
    for (int i = 0; i <= cur; i++) ans += curL;
    curL++;
    k -= cur * (cur + 1) / 2;
  }
  cout << ans << endl;
  return 0;
}
