#include <bits/stdc++.h>
using namespace std;
const int MOD = 1000000007, MOD2 = 1000000009;
const int INF = 0x3f3f3f3f;
const long long BINF = 0x3f3f3f3f3f3f3f3fLL;
int n;
int solve() {
  cin >> n;
  if (n == 0) return cout << "z" << endl, 0;
  char now = 'a';
  int cnt = 0;
  while (n > 0) {
    if (cnt > n) {
      now++;
      cnt = 0;
    }
    n -= cnt++;
    cout << now;
  }
  cout << endl;
  return 0;
}
int main() {
  ios::sync_with_stdio(0);
  solve();
  return 0;
}
