import sys
from heapq import *
input = sys.stdin.readline

def main():
    """ main """
    N = int(input())
    VS = list(map(int, input().split()))
    heapify(VS)
    for _ in range(N-1):
        a, b = heappop(VS), heappop(VS)
        new_item = (a+b)/2
        heappush(VS, new_item)
    print(VS[0])

if __name__ == '__main__':
    main()