import sys
input = sys.stdin.readline

from collections import Counter
from bisect import bisect_left

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

A.sort()

C=Counter(A)


ANS=0

for i in range(len(A)):
    if i>=1 and A[i]==A[i-1]:
        continue
    a=A[i]
    x=bisect_left(A,a*2)

    c=C[a]
    ANS+=c*(c-1)//2 * (x-c)

    #print(a,ANS)

print(ANS)