import sys


def input():
    return sys.stdin.readline()[:-1]


def main():
    N = int(input())
    v = [int(i) for i in input().split()]
    v.sort(reverse=True)
    for i in range(N-1):
        tmp = (v.pop()+v.pop())/2
        v.append(tmp)
        v.sort()
    print(v[0])


if __name__ == '__main__':
    main()
