# ANSHUL GAUTAM
# IIIT-D

from math import *
from copy import *
from string import *				# alpha = ascii_lowercase
from random import *				# l.sort(key=lambda l1:l1[0]-l1[1]) => ex: sort on the basis difference
from sys import stdin
from sys import maxsize
from operator import *				# d = sorted(d.items(), key=itemgetter(1))
from itertools import *
from collections import Counter		# d = dict(Counter(l))
from collections import defaultdict # d = defaultdict(list)

'''

'''

def solve(l):
	k = 0
	n = len(l)
	l = sorted(l)
	while(k < n-1):
		ans = l[0] + l[1]
		zz = ans/2
		l.pop(0)
		l.pop(0)
		l.append(zz)
		k += 1
	return round(l[0],10)

N = int(stdin.readline())
l = list(map(int, stdin.readline().rstrip().split()))
ans = solve(l)
print("%10f"%ans)
