#include <bits/stdc++.h>
using namespace std;
int main() {
  int k;
  cin >> k;
  if (k == 0) return cout << "a\n", 0;
  int i = 1, y = k;
  char c = 'a';
  cout << c;
  while (y > 0) {
    cout << c;
    y -= i;
    i++;
    if (i > y) {
      i = 1;
      c++;
      cout << c;
    }
  }
  return 0;
}
