N = int(input())
A = list(map(int,input().split()))
dic = {}
for i in A:
    if i not in dic:
        dic[i] = 0
    dic[i] += 1

a = [-1]
b = [0]
for ind,val in dic.items():
    a.append(ind)
#    b.append(val)

a.sort()
for i in range(1,len(a)):
    b.append(dic[a[i]])

rui = []
for i,v in enumerate(b):
    if i == 0:
        rui.append(v)
    else:
        rui.append(rui[-1]+v)
a.sort()


from bisect import *
ans = 0
for ind,val in dic.items():
    if val >= 2:
        nex = val*(val-1)//2
        tmp = bisect_left(a,ind*2)-1
        tmp2 = rui[tmp]-val
        ans += tmp2 * nex
print(ans)