N = int(input())
V = list(map(int,input().split()))

V.sort()
ans = 0.

if N == 2:
  ans = sum(V) / 2.
  print(ans)
  exit()
  
for i in range(N):
  if i == 0:
    ans += V[i] / 2.
  else:
    ans += V[i] / pow(2,N-i)
    
print(ans)
         