#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  long long k;
  cin >> k;
  if (k == 0) {
    cout << "a";
    return 0;
  }
  string s;
  char ch = 'a';
  while (k > 0) {
    s += ch;
    long long ct = 1;
    while (k >= ct) {
      s += ch;
      k -= ct;
      ct++;
    }
    ch++;
  }
  cout << s;
  return 0;
}
