HDOJ 2018 母牛的故事

import java.util.Scanner;
class Main{
    public static void main(String args[]){
        long a[] = new long[56];
        a[1]=1;
        a[2]=2;
        a[3]=3;
        for(int i=4;i<56;i++){
            a[i]=a[i-1]+a[i-3];
        }
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            int n = sc.nextInt();
            if(n==0)
               break;
            System.out.println(a[n]);
        }
    }
}