import numpy as np

number = int(input())
input_a_list = list(map(int, input().split()))

input_a_nparray = np.array(input_a_list)
sorted_input_a_nparray = np.sort(input_a_nparray)

max_sum = 0

for t in range(0, number*number):
    sorted_input_a_nparray = np.random.permutation(np.sort(input_a_nparray))

    while len(sorted_input_a_nparray) > 1:
        sorted_input_a_nparray[1] = (sorted_input_a_nparray[0] + sorted_input_a_nparray[1])/2
        sorted_input_a_nparray = np.delete(sorted_input_a_nparray, 0)
    
    if(sorted_input_a_nparray[0] > max_sum):
        max_sum = sorted_input_a_nparray[0]

print(max_sum)