#include <bits/stdc++.h>
using namespace std;
int main() {
  long long i, j, k, l, m, n;
  string tem = "";
  cin >> n;
  char c = 'a';
  if (n == 0)
    cout << "x";
  else
    while (n != 0) {
      long long x = ((-1) + sqrt(1 + (8 * n))) / 2;
      for (i = 0; i <= x; i++) {
        tem += c;
      }
      c++;
      n -= (x * (x + 1)) / 2;
    }
  cout << tem;
}
