# -*- coding: utf-8 -*-
"""
Spyder Editor

This is a temporary script file.
"""
n = int(input())
v = input().split()
v.sort()
sp = 0
d = (int(v[0]) + int(v[1])) / 2
for i in range(2, n):
    d = (d + int(v[i])) / 2
print(d)