#include <bits/stdc++.h>
using namespace std;
int main() {
  int k, i, c;
  cin >> k;
  for (i = 0; i < 26; i++) {
    c = 1;
    while ((c * (c + 1)) / 2 <= k) {
      c++;
    }
    k -= (c * (c - 1)) / 2;
    for (int j = 0; j < c; j++) {
      cout << (char)('a' + i);
    }
  }
  cout << endl;
  return 0;
}
