N = int(input())
a = map(int, input().split())

sorted_list = sorted(a)
print(sorted_list)
num = 0
last_num = 0

for i in range(N):
    if len(sorted_list) == 1:
        if i == 0:
            last_num = sorted_list[num]
        last_num = (sorted_list[num] + last_num) / 2
        break
    x = sorted_list[num]
    y = sorted_list[num+1]
    z = (x + y) / 2
    last_sum = z
    sorted_list.pop(num)
    sorted_list.pop(num)

print(last_num)
