#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
  ios::sync_with_stdio(false), cin.tie(0);
  int k;
  cin >> k;
  if (!k) {
    cout << "wtf\n";
    return 0;
  }
  char cur = 'a';
  string res;
  while (k) {
    ll x = 1;
    while (x * (x - 1) / 2 <= k) ++x;
    --x;
    res += string(x, cur++);
    k -= x * (x - 1) / 2;
  }
  cout << res << '\n';
  return 0;
}
