N = int(input())
v_list = sorted(list(map(int,input().split())))
print(v_list)

sum = 0
a = 0

if N == 1:
    sum += v_list[0]

elif N == 2:
    sum += (v_list[0] + v_list[1])/2

else:
    a = v_list[0] + v_list[1]
    for i in range(N-1):
        sum += a *2 ** (-N + i +1)
     
print(sum)