490 B
490 B
Your library teacher 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 Output: the number of ways you can place red-colored books and blue-colored books onto the bookshelf
Ex: N=3
Input: 3
BB BB
BB BR
BR BB
RB BB
BB RB
RB BR
BR RB
Output: 6