import numpy as np

def set_list(es):
    return len(list(set(es))) == 1

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

if(len(a)==2):
    print((a[0]+a[1])/2)  
elif(len(a)!=2 and set_list(a)):
    print(a[0])
else:
  for i in range(1,n):
    idx = np.argmin(a)
    num1 = a.pop(idx)
    idx = np.argmin(a)
    num2 = a.pop(idx)
    a.append((num1+num2)/2)
	print(a[0])