from math import comb
from bisect import bisect_left
from itertools import accumulate
from collections import defaultdict

dic = defaultdict(int)
N = int(input())
for a in list(map(int, input().split())):
    dic[a] += 1
L = sorted(list(dic.items()))
K, V = zip(*L)
N2 = len(K)
V2 = list(accumulate(V))
ans = 0
for k, v in L:
    if v >= 2:
        a = bisect_left(K, 2 * k)
        ans += comb(v, 2) * (V2[a - 1] - v)
print(ans)