#include <bits/stdc++.h>
using namespace std;
const long double PI = atan(1.0) * 4.0;
const long long int MOD = 1e9 + 7;
const long long int INF = 1e5;
const long double EPS = 0.0000001;
int main() {
  ios_base::sync_with_stdio(false), cin.tie(NULL);
  int a[1005], k;
  a[0] = -1;
  a[1] = 0;
  for (int i = 2; i <= 1005; i++) {
    a[i] = a[i - 1] + i - 1;
  }
  cin >> k;
  if (k == 0) {
    cout << "a" << endl;
    return 0;
  }
  char ch = 'a';
  while (k > 0) {
    int lb = lower_bound(a, a + 1005, k) - a;
    if (a[lb] != k) lb--;
    for (int i = 1; i <= lb; i++) cout << ch;
    k -= a[lb];
    ch++;
  }
  cout << endl;
  return 0;
}
