#include <bits/stdc++.h>
using namespace std;
double tick() {
  static clock_t oldt, newt = clock();
  double diff = 1.0 * (newt - oldt) / CLOCKS_PER_SEC;
  oldt = newt;
  return diff;
}
int main() {
  int k;
  cin >> k;
  char c = 'a';
  string s;
  int x;
  if (k == 0) {
    cout << "a" << endl;
    return 0;
  }
  while (k > 0) {
    x = 1;
    while (1) {
      if (x * (x + 1) / 2 > k) break;
      x++;
    }
    s += string(x, c);
    ++c;
    k -= x * (x - 1) / 2;
  }
  cout << s << endl;
  cerr << "execution time is: " << tick() << "\n";
}
