import math

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

v.sort()

while len(v) > 1:
    a = []
    for i in range(math.ceil(len(v)/2)):
        try:
            a.append((v[i*2]+v[i*2+1])/2)
        except IndexError:
            a.append(v[-1])

    v = a

print(a[0])




