#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  vector<int> tri;
  long long int sum = 0;
  for (int i = 1; i <= 1000; i++) {
    tri.push_back(i * (i + 1) / 2);
  }
  int k;
  cin >> k;
  if (k == 0) {
    cout << "a";
    return 0;
  }
  string ans = "";
  char curr = 'a';
  while (k) {
    int idx = lower_bound(tri.begin(), tri.end(), k) - tri.begin();
    if (tri[idx] == k) {
      ans.append(string(idx + 2, curr));
      curr++;
      k = 0;
    } else {
      idx--;
      ans.append(string(idx + 2, curr));
      curr++;
      k = k - tri[idx];
    }
  }
  cout << ans;
  return 0;
}
