#include <bits/stdc++.h>
using namespace std;
int k;
int a[1000];
string ans;
int main() {
  for (int j = 0; j <= k; ++j) {
  }
  scanf("%d", &k);
  for (int i = 1; i < 1000; ++i) {
    a[i] = i + a[i - 1];
  }
  int idx = lower_bound(a, a + 1000, k) - a;
  int ch = 0;
  for (int i = idx; i >= 1; i--) {
    while (k >= a[i]) {
      k -= a[i];
      for (int j = 0; j < i + 1; j++) ans += char(ch + 'a');
      ch++;
    }
  }
  if (ans.empty()) ans += "a";
  cout << ans;
  return 0;
}
