PROGRAMMING:The problem of rabbit reproduction

It is known that a pair of rabbits can give birth to a pair of rabbits every month, and a pair of rabbits can give birth to a pair of rabbits a month later (for example, a rabbit born in February can give birth in April). That is to say, the logarithm of rabbits is: 1 pair in the first month, 2 pairs in the second month, 3 pairs in the third month, 5 pairs in the fourth month... Suppose that the breeding period of rabbits is two years, and they do not die. So the question is, can you tell the number of rabbits per month?
###Input format:
Enter a number n to represent the nth month, 1 < = n < = 24.
###Output format:
Output the number of rabbits in this month.
###Input example:
```in
four
```
###Output example:
```out
five
```







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