def main():
    N = input()
    in_value = [float(i) for i in input().split(' ')]

    sort_value = sorted(in_value)

    if(N != 1):
        while(len(sort_value) != 1):
            sort_value = [(sort_value.pop(0) + sort_value.pop(0)) / 2] + sort_value
                       
    print(sort_value[0])


if __name__ == "__main__":
    main()