import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Triangle extends JApplet implements ActionListener{
	JPanel inputPanel, outputPanel, mainPanel, appPanel;
	JTextField A,B,out;
	JButton execute;
	
	public void init(){
		A = new JTextField("Input A",10);
		B = new JTextField("Input B", 10);
		
		inputPanel = new JPanel(new BorderLayout(5,5));
		inputPanel.add(A,BorderLayout.NORTH);
		inputPanel.add(B,BorderLayout.SOUTH);
		
		out = new JTextField("Output", 10);
		out.setEditable(false);
		execute = new JButton("Execute");
		execute.addActionListener(this);
		
		outputPanel = new JPanel(new BorderLayout(5,5));
		outputPanel.add(out, BorderLayout.NORTH);
		outputPanel.add(execute, BorderLayout.SOUTH);
		
		mainPanel = new JPanel(new BorderLayout(5,5));
		mainPanel.add(inputPanel, BorderLayout.WEST);
		mainPanel.add(outputPanel, BorderLayout.EAST);
		
		appPanel = new JPanel(new BorderLayout(0,0));
		appPanel.add(mainPanel, BorderLayout.CENTER);
		appPanel.add(Box.createRigidArea(new Dimension(5,0)), BorderLayout.WEST);
		appPanel.add(Box.createRigidArea(new Dimension(5,0)), BorderLayout.EAST);
		appPanel.add(Box.createRigidArea(new Dimension(0,5)), BorderLayout.NORTH);
		appPanel.add(Box.createRigidArea(new Dimension(0,5)), BorderLayout.SOUTH);
		
		setContentPane(appPanel);
		setSize(245,60);
	}

	private long pascalTriangle(long a, long b){
		if(b==0 || b==a){
			return 1;
		}
		if(b==1 || b==a-1){
			return a;
		}
		return pascalTriangle(a-1,b-1)+pascalTriangle(a-1,b);
	}

	public void actionPerformed(ActionEvent arg0) {
		out.setText(
			String.valueOf(
				pascalTriangle(
					Long.parseLong(A.getText()),
					Long.parseLong(B.getText())
				)
			)
		);
	}
}