PROGRAMMING:Xiao AI Kao's recursion
Xiao AI is known as the law all-around king in the world. He has been addicted to reasoning and analysis since he was a child. As long as he can reason or find the problem of law, no matter what knowledge point it examines, he will be right. Xiao AI's amazing reasoning and analysis ability made his friends envious, so they came to him for advice on reasoning methods. Of course, Xiao AI can't teach his friends directly, so they have to test them before they think about it.
The topics are as follows:
Suppose a pair of big rabbits give birth to a pair of small rabbits every month, and each pair of new rabbits gives birth to a cub one month after birth, if the rabbits do not die. In particular, after the first month, an additional pair of big rabbits were introduced (friendly tips: at the beginning, a pair of rabbits gave birth to a pair of small rabbits a month later. At this time, an additional pair of big rabbits were introduced, but no additional rabbits were introduced in the second month 2, 3, 4... Months). If the rabbits did not die. Q: how many pairs of rabbits will there be after the nth month? Come on, quickly gnaw down this problem, you are the next law Almighty king!
###Input format:
Enter an integer n (1 < = n < = 70)
###Output format:
Output the logarithm of the rabbit after the nth month of an integer
###Input sample 1:
```in
one
```
###Output sample 1:
```out
three
```
Example explanation: after the first month, an additional pair was introduced, and the big rabbit gave birth to another pair, 1 + 1 + 1 = 3
###Input sample 2:
```in
two
```
###Output sample 2:
```out
five
```
There are two pairs of big rabbits and one pair of small rabbits after the first month. One month later, two pairs of big rabbits will give birth to two pairs of small rabbits, and one pair of small rabbits is still in the stage of development, so the answer is 2 + 2 + 1 = 5 < br > < br > < br > < br > < br > 2 + 1 = 5
answer：If there is no answer, please comment
The topics are as follows:
Suppose a pair of big rabbits give birth to a pair of small rabbits every month, and each pair of new rabbits gives birth to a cub one month after birth, if the rabbits do not die. In particular, after the first month, an additional pair of big rabbits were introduced (friendly tips: at the beginning, a pair of rabbits gave birth to a pair of small rabbits a month later. At this time, an additional pair of big rabbits were introduced, but no additional rabbits were introduced in the second month 2, 3, 4... Months). If the rabbits did not die. Q: how many pairs of rabbits will there be after the nth month? Come on, quickly gnaw down this problem, you are the next law Almighty king!
###Input format:
Enter an integer n (1 < = n < = 70)
###Output format:
Output the logarithm of the rabbit after the nth month of an integer
###Input sample 1:
```in
one
```
###Output sample 1:
```out
three
```
Example explanation: after the first month, an additional pair was introduced, and the big rabbit gave birth to another pair, 1 + 1 + 1 = 3
###Input sample 2:
```in
two
```
###Output sample 2:
```out
five
```
There are two pairs of big rabbits and one pair of small rabbits after the first month. One month later, two pairs of big rabbits will give birth to two pairs of small rabbits, and one pair of small rabbits is still in the stage of development, so the answer is 2 + 2 + 1 = 5 < br > < br > < br > < br > < br > 2 + 1 = 5
answer：If there is no answer, please comment