#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1 * 1000 + 10;
int main() {
  ios::sync_with_stdio(false);
  int k;
  cin >> k;
  if (k == 0) {
    cout << "a" << endl;
    return 0;
  }
  string ans;
  int c = 0;
  while (k > 0) {
    int sum = 0, i = 1;
    for (; true; i++) {
      if (sum + i > k) {
        k -= sum;
        break;
      }
      sum += i;
    }
    while (i > 0) {
      ans.push_back('a' + c);
      i--;
    }
    c++;
  }
  cout << ans << endl;
  return 0;
}
