import sys
import os


def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    N = int(sys.stdin.buffer.readline().rstrip())
    V = list(map(int, sys.stdin.buffer.readline().split()))
    V.sort(reverse=True)

    ret = 0
    for n in range(N-1):
        if ret == 0:
            ret = (V[n] + V[n+1]) / 2
        else:
            ret = (ret + V[n+1]) / 2
    print(ret)


if __name__ == '__main__':
    main()
