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