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

from collections import defaultdict
from bisect import bisect_left

d = defaultdict(int)
for i in range(N):
    d[A[i]] += 1

cnt = sorted(list(d.items()))
S = [0] * (len(cnt) + 1)
for i in range(len(cnt)):
    S[i+1] = S[i] + cnt[i][1] * (cnt[i][1] - 1) // 2

ans = 0
for i in range(len(cnt)):
    ans += cnt[i][1] * (S[-1] - S[bisect_left(cnt, (cnt[i][0]//2+1,))] - cnt[i][1] * (cnt[i][1] - 1) // 2)

print(ans)