#include <bits/stdc++.h>
using namespace std;
int n;
string s;
int main() {
  scanf("%d", &n);
  char c = 'a';
  if (n == 0) s = 'a';
  while (n) {
    int m = 1;
    while (m * (m + 1) / 2 <= n) m++;
    n -= m * (m - 1) / 2;
    while (m) s += c, m--;
    c++;
  }
  cout << s << endl;
  return 0;
}
