import decimal,math
from collections import Counter,defaultdict
from fractions import gcd
from bisect import bisect_right,bisect_left
decimal.getcontext().prec = 10
N=int(raw_input())

arr=map(int,raw_input().split())
arr=sorted(arr)
# l = float(pow(2,N-1))
# ans=(arr[0]+arr[1])/l
# print ans
for i in range(1,N):
	arr[i] = (arr[i]+arr[i-1])/2.0
	# print arr
print arr[-1]	
