题解 | #统计每个月兔子的总数#

public class Main{

	public static void main(String[] args) {		Scanner sc = new Scanner(System.in);

		while(sc.hasNext()){

			int[] arr = new int[31];

			int a = sc.nextInt();

			int count1 = 1;

			int count2 = 0;

			int count3 = 0;

			int tmp;

			arr[0]=1;

			for(int i=1;i<31;i++){

				count3+=count2;

				count2=count1;

				count1=count3;

				arr[i] = count1+count2+count3;

			}

			System.out.println(arr[a-1]);

		}

	}

}