#!/usr/bin/env python

N = input()
N = int(N)

v = []
v = input().split()
v = [int(n) for n in v]
v.sort()

v[0] = int(v[0])

for i in range(N - 1) :
	v[i + 1] = (int(v[i]) + int(v[i + 1])) / 2

print(v[N - 1])
