def N_M_add(N, M):
    """
    回文数加减器：N是进制数，M是要求的数  2<=N<=10
    N为int型，M为str型
    """
    flag = 0
    lenM = len(M)  # M的长度
    M_re = M[::-1]  # M的逆序数
    s_list = []
    for i in range(1, lenM + 1):
            t = 0
            k = int(M_re[-i]) + int(M[-i]) + flag
            ys = k % N
            if k >= N:
                flag = 1
            else:
                flag = 0
            s_list.insert(-t, '{}'.format(ys))  # 插到列表后面
            if (i == lenM and flag == 1):
                s_list.insert(0, '1')  # 插到列表后面
            t = t + 1
    s = ''.join(s_list)
    return s


i = 1
N = input()  # N是进制数
M = input()  # M是要求的数
a = []
while (1):
    suc_flag = 1
    if N == '16':
        M1 = str(int("{}".format(M), 16))  # 先把这个数转成10进制
        conf = N_M_add(10, M1)
        conf_1 = hex(int(conf))  # 再把结果转回16进制
        conf_1 = conf_1[-2:]  # 去除前缀的0x
        if conf_1 == conf_1[::-1]:
            break
        else:
            i = i + 1
            M = conf_1

        if i > 30:
            suc_flag = 0
            i = 0
            break
    else:
        conf = N_M_add(int(N), M)
        if conf == conf[::-1]:
            break
        else:
            i = i + 1
            M = conf

        if i > 30:
            suc_flag = 0
            i = 0
            break

if (suc_flag):
    print('STEP={}'.format(i))
else:
    print('Impossible!')

怎么把最后一个回车读入去掉啊啊啊啊啊，我太菜了....