import bisect
from collections import Counter
from math import comb
N = int(input())
A = sorted(list(map(int,input().split())))

ac = Counter(A)
ans = 0
for i in ac:
    if(ac[i] >= 2):
        MAX = i*2
        ans += comb(ac[i],2) * (bisect.bisect_left(A,MAX) - ac[i])
print(ans)