#include <bits/stdc++.h>
using namespace std;
int main() {
  int k;
  cin >> k;
  int re = 1, various = 0;
  if (!k) printf("ab");
  various = 0;
  while (k) {
    re = 1;
    while (re * (re - 1) / 2 <= k) re++;
    re--;
    k -= re * (re - 1) / 2;
    for (int i = 1; i <= re; ++i) printf("%c", 'a' + various);
    various++;
  }
  printf("\n");
  return 0;
}
