from collections import defaultdict
import bisect
n=int(input())
L=list(map(int,input().split()))
L.sort()
D=defaultdict(int)
for e in L:
	D[e]+=1

ans=0
for k,v in D.items():
	if 2<=v:
		id=bisect.bisect_left(L,k*2)
		ans+=(v*(v-1)//2) * (id-v)
print(ans)