Java program to print tribonacci number

NOTE:- A series in which the sum of the first three number is equal to fourth.

import java.util.Scanner;
public class tribonacci
{
public static void main(String[]args)
{
Scanner sc=new Scanner (System.in);
System.out.println("Enter number of terms");
int num=sc.nextInt();
int a=0;
int b=1;
int c=1;
int d;
int i=4;
System.out.print(a+",");
System.out.print(b+",");
System.out.print(c+",");
while(i<=num)
{
d=a+b+c;
System.out.print(d+",");
a=b;
b=c;
c=d;
i++;
}

}
}