from itertools import accumulate
from collections import Counter
import math
import bisect

N=int(input())
A=list(map(int, input().split()))
C=Counter(A)
A=sorted(set(A))
mem=[]
for i in A:
    mem.append(C[i])

mem=list(accumulate(mem))

ans=0
for i in range(len(A)):
    idx = bisect.bisect_left(A, A[i]*2)
    ans += math.comb(C[A[i]],2)*(mem[idx-1]-C[A[i]])

print(ans)