from collections import Counter
from bisect import bisect_left, bisect_right

def encode(x,y):
    return x*(10**6) + y

def decode(val):
    return divmod(val)

n = int(input())
alist = list(map(int, input().split()))

co = Counter(alist)
le = len(co)

keys = sorted(co.keys())

values = [co[keys[i]] for i in range(le)]

rui = [values[i] for i in range(le)]

for i in range(le-1):
    rui[i+1] += rui[i]

ans = 0
for i in range(le):
    key = keys[i]
    val = values[i]
    if val == 1:
        continue

    loc = bisect_left(keys, key*2)
    if loc <= 1:
        continue

    else:
        num = rui[loc-1] - val

        ans += val * (val-1) * num //2
print(ans)