Anyone here good with programming Java?

Currently I'm in a beginner's course for programming Java and so far it's going well. However I can't seem to figure out this tiny problem in one of my programs.

Code:

import static java.lang.System.*;
import java.util.*;
import java.awt.*;
public class Java1409
{
	public static void main(String[] args)
	{
		Stairs climb = new Stairs();
		climb.input();
		climb.process();
		climb.output();
   	}
}

class Stairs
{
	int numStairs;
	int numTripsPerDay;
	int numYears;
	
	int totalPerDay;
	int totalPerYear;
	int grandTotal;
	
	void input()
	{
		Scanner scan = new Scanner(in);
		out.println("How many stairs are on your staircase?");
		numStairs = scan.nextInt();
		
		out.println("How many trips a day do you make up and down the steps?");
		numTripsPerDay = scan.nextInt();
		
		out.println("How many years have you lived in your house?");
		numYears = scan.nextInt();   		
	}
	
	void process()
	{
		totalPerDay = numStairs * 2 * numTripsPerDay;
		totalPerYear = totalPerDay * 365;
		grandTotal = totalPerYear * numYears;
	}
	
	void output()
	{	
		out.println();
		out.println("Stairs climbed per day: " + totalPerDay );
		out.println("Stairs climbed per year: " + totalPerYear );
		out.println("Stairs climbed in your lifetime: " + grandTotal );
		out.println();
	}
}

That's the code I'm using and it works just fine. But my teacher won't give me credit for it unless I let the final input have commas in it.

My current output:


So basically, I just need to have it say like 21,900 and not 21900.