题解 | 跳台阶扩展问题

num = int(input())


def jumpFloorII(number):
    # number = 0    没有
    # number = 1    1
    # number = 2    2
    # number = 3    4
    # number = 4    8
    # number = n    2*(n-1)
    # f(n) = f(n-1)+ f(n-2)+...+f(1)
    # f(n-1) = f(n-2)+...+f(1)
    # f(n) = 2f(n-1)    n>1
    if number == 1:
        return 1
    ret = 1
    a = 1
    for i in range(2, number + 1):
        ret = 2 * a
        a = ret
    return ret
    # return pow(2,number)


print(jumpFloorII(number=num))