#include <bits/stdc++.h>
using namespace std;
const int N = 3e5 + 2, lg = 19;
int a[40];
int main() {
  int k;
  cin >> k;
  int j = 0;
  for (int i = 0; i < 28; i++) {
    a[i] = 1;
  }
  if (k == 0) {
    cout << 'a' << endl;
    return 0;
  }
  while (k > 0) {
    if (k - a[j] >= 0) {
      k -= a[j];
      a[j]++;
    } else {
      j++;
    }
  }
  for (int i = 0; i < 26; i++) {
    if (a[i] > 1) {
      while (a[i] > 0) {
        a[i]--;
        cout << char(i + 'a');
      }
    }
  }
  return 0;
}
