Tiling a 3-by-N Wall

There is a rectangular wall with height 3 and width $N$. You want to cover the entire wall with domino tiles of size $2\times1$ or $1\times2$.

Tiles must not overlap, and no tile may extend outside the wall. Find the number of different ways to tile the wall.

The first line contains an integer $N$. $(1 \le N \le 30)$

Print the number of ways to tile a $3\times N$ wall.

The figure below shows one tiling of a $3\times12$ wall.