import itertools

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

result = []
for v in itertools.permutations(list, N):
    avg = 0
    for num in v:
        if avg == 0:
            avg = num
        else:
            avg = (num + avg) / 2
    result.append(avg)

print(max(result))
