#include <bits/stdc++.h>
using namespace std;
const long long cls = 1e9 + 7;
const int maxn = 2e5 + 10;
const double eps = 1e-13;
const double pi = acos(-1.0);
using namespace std;
int main() {
  int n;
  cin >> n;
  string s = "";
  if (n == 0) {
    cout << "f" << endl;
    return 0;
  }
  int sum = 0;
  for (char i = 'a'; i <= 'z'; i++) {
    if (sum == n) {
      break;
    } else {
      int num = 1;
      s += i;
      while (sum + num <= n) {
        s += i;
        sum += num;
        num++;
      }
    }
  }
  cout << s << endl;
  return 0;
}
