#2TriangleArea

import java.util.Scanner;

public class TriangleArea {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int xA = scan.nextInt();
        int yA = scan.nextInt();
        int xB = scan.nextInt();
        int yB = scan.nextInt();
        int xC = scan.nextInt();
        int yC = scan.nextInt();
        calculateTriangleArea(xA, yA, xB, yB, xC, yC);
    }

    private static void calculateTriangleArea(int xA, int yA, int xB, int yB, int xC,
            int yC) {
        int area = 0;
        area = Math.abs(Math.round(((xA*(yB - yC)) + (xB*(yC - yA)) + (xC*(yA - yB))) / 2));
        printResult(area);
    }

    private static void printResult(int number) {
        System.out.println(number);
    }
}