import heapq
import math


def solve(n, v):
    heapq.heapify(v)
    nn = math.ceil(n / 2)

    for i in range(nn):
        x = heapq.heappop(v)
        y = heapq.heappop(v)
        z = (x + y) / 2
        heapq.heappush(v, z)

    return heapq.heappop(v)


n = int(input())
v = list(map(int, input().split()))

print(solve(n, v))
