easyctf-2017/library/description.md

Your librarian has a 2-row bookshelf that can contain N books in each row. She wants to know the number of ways that she can fill the bookshelf with red-colored books and blue-colored books such that no 2 red-colored books are adjacent to each other (horizontally or vertically).

Input: the integer, N (1<=N<=2^1024)

Output: the number of ways you can place red-colored books and blue-colored books onto a N-column bookshelf. Since this number might be really big, output it mod 10^9+7.

Example:
Input: 2

Your valid bookshelf layouts are:
```
BB
BB

BB
BR

BR
BB

RB
BB

BB
RB

RB
BR

BR
RB
```
Therefore, 
Output: 7
Update description.md how 2 speel 2016-11-03 18:40:00 +00:00			`Your librarian has a 2-row bookshelf that can contain N books in each row. She wants to know the number of ways that she can fill the bookshelf with red-colored books and blue-colored books such that no 2 red-colored books are adjacent to each other (horizontally or vertically).`
Create description.md 2016-11-03 18:36:52 +00:00
Update description.md 2016-11-03 19:46:43 +00:00			`Input: the integer, N (1<=N<=2^1024)`
Update description.md 2016-11-03 18:37:58 +00:00
Update description.md 2017-03-11 06:11:38 +00:00			`Output: the number of ways you can place red-colored books and blue-colored books onto a N-column bookshelf. Since this number might be really big, output it mod 10^9+7.`
Create description.md 2016-11-03 18:36:52 +00:00
Update description.md 2017-03-11 01:19:43 +00:00			`Example:`
Update description.md 2017-03-11 06:11:38 +00:00			`Input: 2`
Create description.md 2016-11-03 18:36:52 +00:00
Update description.md 2017-03-11 01:19:43 +00:00			`Your valid bookshelf layouts are:`
			```
Create description.md 2016-11-03 18:36:52 +00:00			`BB`
			`BB`

			`BB`
			`BR`

			`BR`
			`BB`

			`RB`
			`BB`

			`BB`
			`RB`

			`RB`
			`BR`

			`BR`
			`RB`
Update description.md 2017-03-11 01:19:43 +00:00			```
			`Therefore,`
Update description.md 2017-02-03 22:59:05 +00:00			`Output: 7`