package Homework;
import java.awt.Point;
import java.util.Scanner;

public class TriangleArea {
	public static void main(String[] args) {
		Scanner reader = new Scanner(System.in);
		Point pointA = new Point(reader.nextInt(),reader.nextInt());
		Point pointB = new Point(reader.nextInt(),reader.nextInt());
		Point pointC = new Point(reader.nextInt(),reader.nextInt());

		System.out.println(TriangleArea(pointA, pointB, pointC));
	}

	private static int TriangleArea(Point pointA, Point pointB, Point pointC) {
																			//(Ax*(By-Cy)+Bx*(Cy-Ay)+Cx*(Ay-By))/2;
        int result = (int) ((pointA.getX()*(pointB.getY()- pointC.getY())+ pointB.getX()*(pointC.getY()-pointA.getY())+pointC.getX()*(pointA.getY()-pointB.getY()))/2);
        if (result < 0){
        	return  -result;

        }
		return result;
}
	}