N=int(input())
A=list(map(int,input().split()))
from bisect import bisect_right
A.sort()
result=0
T={}
for i in range(N):
  x=A[i]
  if not x in T:
    T[x]=1
  else:
    T[x]+=1
for x in T:
  n=T[x]
  count=n*(n-1)//2
  pos1=bisect_right(A,2*x-1)
  ans=(pos1-n)*count
  result+=ans
print(result)