from collections import defaultdict

N = int(input())
A = list(map(int, input().split()))
D = defaultdict(int)
for a in A:
    D[a] += 1

A.sort()
B = list(D.keys())
B.sort()
n = 0
ans = 0
for b in B:
    if D[b] >= 2:
        while n < N-1 and A[n+1] < 2*b:
            n += 1
            
        ans += (D[b]*(D[b]-1)//2) * (n+1 - D[b])
print(ans)