#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
const double PI = 3.14159265359;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int k;
  cin >> k;
  vector<int> val(1000, 0);
  for (int i = 1; i < 1000; i++) {
    val[i] = val[i - 1] + i - 1;
    for (int j = 1; j < i; j++) {
      val[i] = min(val[i], val[j] + val[i - j] + j * (i - j));
    }
  }
  string ans;
  char c = 'a';
  while (k) {
    auto it = lower_bound(val.begin(), val.end(), k);
    if (*it > k) it--;
    int num = *it;
    string s(it - val.begin(), c);
    ans += s;
    c++;
    k -= num;
  }
  if (!ans.size()) ans = "a";
  cout << ans;
  return 0;
}
