#include <bits/stdc++.h>
using namespace std;
int main() {
  int k;
  cin >> k;
  char a[200005];
  int j = 0, ans = 0, count1 = 0, count = 0;
  char x = 'a', f;
  if (k == 0)
    cout << 'a' << endl;
  else {
    for (int i = 0; i < 26; i++) {
      if (ans == k) break;
      f = char(int(x));
      while (ans <= k) {
        a[j] = f;
        j++;
        ans += count;
        count++;
      }
      if (ans > k) {
        ans -= count - 1;
        count = 0;
        j--;
        x = int(x) + 1;
        i++;
      } else
        break;
    }
    for (int i = 0; i < j; i++) cout << a[i];
    cout << endl;
  }
  return 0;
}
