from collections import Counter
from bisect import bisect_left


N = int(input())
A = list(map(int, input().split()))
A.sort()
cnt = Counter(A)
ans = 0
for a, v in sorted(cnt.items()):
    ans += v * (v - 1) // 2 * (bisect_left(A, 2 * a) - v)
print(ans)