02TriangleArea

import java.util.Scanner;


public class TriangleArea {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        String aAsString = input.nextLine();
        String[] pointA = aAsString.split(" ");
        String bAsString = input.nextLine();
        String[] pointB = bAsString.split(" ");
        String cAsString = input.nextLine();
        String[] pointC = cAsString.split(" ");
        int ax = Integer.parseInt(pointA[0]);
        int ay = Integer.parseInt(pointA[1]);
        int bx = Integer.parseInt(pointB[0]);
        int by = Integer.parseInt(pointB[1]);
        int cx = Integer.parseInt(pointC[0]);
        int cy = Integer.parseInt(pointC[1]);
        int area = (ax*(by-cy) + bx*(cy-ay) + cx*(ay-by))/2;
        if(area>0){
        System.out.println(area);

        }
        else {
            System.out.println(area*-1);
        }


    }

}