# coding:utf-8
import sys
def main():
    N = int(input())
    lists = list(map(float, input().split()))
    lists.sort()

    for i in range(N-1):
        new_guzai = (lists[0] + lists[1]) / 2

        for _ in range(2):
            lists.pop(0)

        lists.append(float(new_guzai))
        if len(lists) ==1:
            print(lists[0])
            sys.exit()


if __name__ == '__main__' :
    main()