#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e4;
int arr[MAXN];
int main() {
  for (int i = 1; i < MAXN; i++) arr[i] = arr[i - 1] + i;
  int k;
  cin >> k;
  char temp = 'a';
  if (k == 0) putchar(temp);
  while (k) {
    int cnt = lower_bound(arr, arr + MAXN, k) - arr;
    if (arr[cnt] > k) cnt--;
    k -= arr[cnt];
    cnt++;
    while (cnt--) putchar(temp);
    temp++;
  }
  return 0;
}
