#include <bits/stdc++.h>
using namespace std;
int a[10000];
int main() {
  a[0] = 0, a[1] = 0;
  for (int i = 2; i <= 1000; i++) {
    a[i] = a[i - 1] + i - 1;
  }
  int k;
  cin >> k;
  char ch = 'a';
  if (k == 0)
    puts("a");
  else {
    while (k) {
      int x = lower_bound(a + 1, a + 1000, k) - a;
      if (a[x] > k) x--;
      k -= a[x];
      for (int i = 0; i < x; i++) {
        printf("%c", ch);
      }
      ch++;
    }
  }
  return 0;
}
