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)

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)

print(sorted_input_a_nparray[0])