Recursion 2:Staircase

public class Solution
{
    public static int staircase(int n)
    {
        if(n<0)
            return 0;
        if(n==0)
            return 1;
        int op1=staircase(n-1);
        int op2=staircase(n-2);
        int op3=staircase(n-3);
        return op1+op2+op3;


    }

}