N=int(input())
v=list(map(int,input().split()))
s=0
v.sort()
if len(v)==1:
  print(v[0])
elif len(v)==2:
  print(sum(v)/2)
else:
  s+=(v[0]+[1])/(2**N-1)
  for j in range(2,N):
    s+=v[j]/(2**N-j)
print(s)
