/* -*- coding: utf-8 -*-
 *
 * 3128.cc:  No.3128 Isosceles Triangle - yukicoder
 */

#include<cstdio>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_N = 300000;

/* typedef */

using ll = long long;

/* global variables */

int as[MAX_N], cs[MAX_N];
ll css[MAX_N + 1];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", as + i);

  sort(as, as + n);
  int m = 0;
  for (int i = 0; i < n;) {
    int j = i;
    while (i < n && as[j] == as[i]) i++;
    as[m] = as[j], cs[m] = i - j, m++;
  }
  for (int i = 0; i < m; i++) css[i + 1] = css[i] + cs[i];
  //for (int i = 0; i < m; i++) printf(" %d,%d", as[i], cs[i]); putchar('\n');

  ll sum = 0;
  for (int i = 0; i < m; i++)
    if (cs[i] >= 2) {
      ll nc2 = (ll)cs[i] * (cs[i] - 1) / 2;
      int j = lower_bound(as, as + m, as[i] * 2) - as;
      sum += nc2 * (css[j] - cs[i]);
    }

  printf("%lld\n", sum);
  
  return 0;
}