n=int(input())
a=list(map(int,input().split()))
z=sorted(set(a))
d={v:i for i,v in enumerate(sorted(set(a)))}
c=[0]*len(d)
for v in a:
  c[d[v]]+=1
cc=[c[i]*(c[i]-1)//2 for i in range(len(c))]
ccc=cc[:]
for i in reversed(range(len(cc)-1)):
  ccc[i]+=ccc[i+1]
from bisect import bisect_right
g=0
for i in range(len(z)):
  p=bisect_right(z,z[i]//2)
  g+=c[i]*(ccc[p]-cc[i])
print(g)