说明：   已知一对兔子，每个月可以生一对小兔，而小兔过一个月后也可以生一对小兔。即兔子的对数是：第一个月1对，第二个月2对，第三个月3对，第四个月5对，……，假设兔子的剩余期是12个月，并且不死 ，问一年后，这对兔子有多少对活着的后代？
(Are known to a pair of rabbits, a pair of rabbit health every month, while the rabbit can be a month after a pair of rabbit health. Namely, the number of pairs of rabbits are: 1 on the first month, the first month two pairs, the first three months, three pairs, the first four months of 5 pairs ... ..., assuming that the rabbit with a maturity of 12 months, and die, Q. A year later, this is the number of pairs of rabbits alive for future generations?)