import math
n = int(input())
a = list(map(int, input().split()))
num = 0
a.sort()
tem = math.ceil(n/2)

if n%2 != 0:
    for i in range(n-1):
        num += a[i]
    print((num/(2**tem))+(a[-1]/2))
else:
    print(sum(a)/(2**tem))