#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9, MOD = 1e9 + 7;
const long double EPS = 1e-9, PI = acos(-1);
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int k;
  cin >> k;
  if (!k) {
    cout << "privet" << endl;
    return 0;
  }
  set<int> nums;
  unordered_map<int, int> translate;
  string answer;
  char print = 'a';
  for (int i = 1; i * (i + 1) <= 2 * k; ++i) {
    nums.insert(i * (i + 1) / 2);
    translate[i * (i + 1) / 2] = i + 1;
  }
  while (k && print <= 'z') {
    int now = *(--upper_bound(nums.begin(), nums.end(), k));
    for (int i = 0; i < translate[now]; ++i) answer += print;
    k -= now;
    print++;
  }
  cout << answer << endl;
  return 0;
}
