#include <bits/stdc++.h>
int k;
int num[26];
char res[100010];
int resL;
void solve() {
  int i, j;
  int sum;
  for (i = 0; i < 26; i++) {
    sum = 0;
    j = 1;
    while (1) {
      sum += j - 1;
      if (sum > k) break;
      j++;
    }
    num[i] = j - 1;
    k -= sum - (j - 1);
    if (k == 0) break;
  }
  resL = 0;
  for (i = 0; i < 26; i++) {
    if (num[i] == 0) break;
    for (j = 0; j < num[i]; j++) {
      res[resL] = 'a' + i;
      resL++;
    }
  }
  res[resL] = 0;
  printf("%s\n", res);
}
int main() {
  scanf("%d", &k);
  solve();
  return 0;
}
