题解 | #统计每个月兔子的总数#

while True:
    try:
        month = int(input())
        big_rabbit = 0 #大兔子数目
        small_rabbit_1 = 1 #刚生下来的小兔子数目
        small_rabbit_2 = 0 #快长大的小兔子数目
        rabbit_num = []
        for i in range(31):
            if(i == 0): #第一个月，刚买回来一只小兔子
                big_rabbit = 0
                small_rabbit_1 = 1
                small_rabbit_2 = 0
                rabbit_num.append(small_rabbit_1 + small_rabbit_2 + big_rabbit)
            else: #后面的每个月
                big_rabbit += small_rabbit_2 #中兔子变大兔子
                small_rabbit_2 = 0 #中兔子没了
                small_rabbit_2 = small_rabbit_1 #小兔子变中兔子
                small_rabbit_1 = 0
                small_rabbit_1 = big_rabbit #大兔子生小兔子
                rabbit_num.append(small_rabbit_1 + small_rabbit_2 + big_rabbit) #每个月总数
        print(rabbit_num[month - 1]) #输出需要的某个月的兔子总数
    except:
        break