UVA - 10918 - Tri Tiling (Java Solution)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringBuffer sb = new StringBuffer("");
        long arr[] = new long[31];
        long arr2[] = new long[31];
        arr[0] = arr2[1] = 1;
        for (int i = 2; i < arr.length; i++) {
            arr[i] = arr[i - 2] + 2 * arr2[i - 1];
            arr2[i] = arr[i - 1] + arr2[i - 2];
        }
        while (true) {
            int x = Integer.parseInt(br.readLine());
            if (x < 0) {
                break;
            }
            if (x % 2 == 1) {
                sb.append("0\n");
            } else {
                sb.append(arr2[x] + arr[x]).append("\n");
            }
        }
        System.out.print(sb);
    }
}