n = int(input())
inputs = [int(i) for i in raw_input().split()]

from fractions import Fraction

def max_remaining(inputs):
    inputs.sort()

    current = list(inputs)
    while len(current) > 1:
        next_list = []
        for i in range(0, len(current)-1, 2):
            next_list.append(Fraction(current[i] + current[i+1], 2))

        if len(current) % 2 == 1:
            next_list.append(current[-1])

        current = list(next_list)
        # print current

    print float(current[0])

max_remaining(inputs)