#include <bits/stdc++.h>
int a[(1010)];
int main() {
  for (int i = 0; i < (1010); ++i) {
    a[i] = i * (i - 1) / 2;
  }
  int k;
  scanf("%d", &k);
  if (!k) {
    printf("a\n");
    return 0;
  }
  std::string ans;
  int now = 0;
  while (k) {
    int x = std::upper_bound(a, a + (1010), k) - a - 1;
    for (int i = 1; i <= x; ++i) {
      ans += 'a' + now;
    }
    ++now;
    k -= a[x];
  }
  std::cout << ans << std::endl;
  return 0;
}
