N=int(input())
A=list(map(int, input().split()))
A=sorted(A)
D={}
for a in A:
  if a not in D:
    D[a]=0
  D[a]+=1
  
C=sorted(list(set(A)))
E=[0]
for c in C:
  E.append(E[-1]+D[c])

ans=0
import bisect
for d in D:
  if D[d]==1:
    continue 
  dd=bisect.bisect_left(C,2*d)
  a=D[d]*(D[d]-1)//2 
  b=E[dd]-D[d]
  ans+=a*b 
print(ans)