题目：古典问题：有一对兔子，从出生后第3个月起每个月都生一对兔子，小兔子长到第三个月后每个月又生一对兔子，假如兔子都不死，问每个月的兔子总数为多少？-Topic: classical question: have a rabbit, from birth after 3 months on every month were born a rabbit, little rabbit to the third month after smaller every month and born a ra