def calculate(arr):

    if len(arr) == 1:
        return arr[0]

    if len(arr) == 2:
        return (arr[0] + arr[1]) / 2

    result = (calculate(arr[:-2]) + (arr[-1] + arr[-2])/2) / 2

    return result

def rank(arr):
    lastIndex = len(arr) - 1
    while lastIndex > 0:
        for i in range(lastIndex):
            if arr[i + 1] > arr[i]:
                tmp = arr[i + 1]
                arr[i + 1] = arr[i]
                arr[i] = tmp

        lastIndex = lastIndex - 1
    return arr

N = int(input())
S = input().split(" ")
arr = list(map(int, list(S)))

arr2 = rank(arr)

result = calculate(list(arr2))
print(int(result))