#include <bits/stdc++.h>
using namespace std;
const long long inf = (long long)4e+18;
int main() {
  srand(1373737);
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n;
  cin >> n;
  if (n == 0) {
    cout << "a";
    return 0;
  }
  vector<long long> arr;
  arr.push_back(0ll);
  arr.push_back(0ll);
  for (long long i = 2ll;; i++) {
    if (i % 10000 == 0) break;
    if (i % 2 == 0)
      arr.push_back(arr[i / 2] + arr[i / 2] + (i / 2ll) * (i / 2ll));
    else
      arr.push_back(arr[i / 2] + arr[i / 2 + 1] + (i / 2ll) * (i / 2ll + 1ll));
  }
  int now = 0;
  string ans = "";
  while (n > 0) {
    int p = upper_bound(arr.begin(), arr.end(), n) - arr.begin() - 1;
    for (int i = 0; i < p; i++) ans += (char)(now + 'a');
    n -= arr[p];
    now++;
  }
  cout << ans;
  return 0;
}
