Tri Tiling - Problem Statement

Count ways to tile a $3 \times n$ rectangle with $1 \times 2$ dominoes. Input Format: - Multiple test cases, one per line.

Each line contains integer $n$ ($0 \leq n \leq 30$) - Terminates when $n = -1$ Output: One answer per line. What to notice: - For odd $n$, answer is $0$ (can't tile $3 \times \text{odd}$) - For even $n$: $f(n) = 4f(n-2) - f(n-4)$ - Base cases: $f(0) = 1$, $f(2) = 3$