#include <bits/stdc++.h>
using namespace std;
int mod = 1000000007;
int main() {
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  if (n == 0) {
    cout << 'a' << endl;
    return 0;
  }
  char c = 'a';
  string s = "";
  while (n) {
    int i = 2;
    for (; i * (i - 1) / 2 <= n; i++)
      ;
    --i;
    n -= i * (i - 1) / 2;
    for (int j = 0; j < (int)(i); ++j) {
      s += c;
    }
    ++c;
  }
  cout << s;
  return 0;
}
