Problem 2. Triangle Area

import java.util.Scanner;


public class TriangleArea {

	public static void main(String[] args) {

		Scanner input = new Scanner(System.in);

		double firstX = input.nextDouble();
		double firstY = input.nextDouble();

		double secondX = input.nextDouble();
		double secondY = input.nextDouble();

		double thirdX = input.nextDouble();
		double thirdY = input.nextDouble();

		double area = (firstX*(secondY-thirdY) + secondX*(thirdY-firstY) + thirdX*(firstY-secondY))/2;
		System.out.println(Math.abs(area));
		input.close();
	}

}