#include <bits/stdc++.h>
using namespace std;
int a[1000005];
int main() {
  memset(a, 0, sizeof(a));
  int num = 0;
  for (int i = 1; i <= 100005; i++) {
    a[i] = a[i - 1] + i;
    num = i;
    if (a[i] > 100005) break;
  }
  int k;
  scanf("%d", &k);
  if (k == 0) {
    printf("ab\n");
    return 0;
  }
  int vis[26] = {0}, numm = 0;
  for (int i = num; i >= 0; i--) {
    if (k >= a[i]) {
      vis[numm++] = i + 1;
      k -= a[i];
      i++;
    }
    if (k == 0) break;
  }
  for (int i = 0; i < numm; i++) {
    for (int j = 0; j < vis[i]; j++) {
      printf("%c", i + 'a');
    }
  }
  printf("\n");
  return 0;
}
