from bisect import bisect_left
from collections import Counter
from itertools import accumulate

N = int(input())
A = list(map(int, input().split()))

values, counts = zip(*sorted(Counter(A).items()))
acc_counts = [0] + list(accumulate(counts))

ans = 0

for i, v in enumerate(values):
    idx = bisect_left(values, 2 * v)
    ans += acc_counts[idx] * counts[i] * (counts[i] - 1) // 2
    ans -= counts[i] * counts[i] * (counts[i] - 1) // 2

print(ans)