#include <bits/stdc++.h>
using namespace std;
int K;
int A[555];
vector<int> V;
int main() {
  cin >> K;
  for (int i = 1; i < 555; i++) A[i] = (i * (i - 1)) / 2;
  if (K == 0) {
    cout << "a" << endl;
    return 0;
  }
  while (K) {
    int q = 0;
    for (int i = 1; i < 555 - 1; i++)
      if (A[i + 1] > K) {
        q = i;
        break;
      }
    V.push_back(q);
    K -= A[q];
  }
  char ch = 'a';
  string ans = "";
  for (auto r : V) {
    for (int i = 1; i <= r; i++) ans += ch;
    ch++;
  }
  cout << ans << endl;
  return 0;
}
