from collections import*
from bisect import*
n,*a=map(int,open(0).read().split())
c=Counter(a)
cs=sorted(c)
s=[0]
for k in cs:
  v=c[k]
  s+=s[-1]+v*(v-1)//2,
ans=0
for i in a:
  m=i//2
  j=bisect(cs,m)
  ans+=s[-1]-s[j]
  if m<=i:
    ans-=c[i]*(c[i]-1)//2
print(ans)