using static System.Math;
using System;

public class Hello
{
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var a = new (int x, int y)[3];
        for (int i = 0; i < 3; i++)
        {
            a[i] = (int.Parse(line[i * 2]), int.Parse(line[i * 2 + 1]));
        }
        getAns(a);
    }
    static int calc((int x, int y)[,] z, int i, int j, int k)
    {
        var x1 = z[0, i].x;
        var y1 = z[0, i].y;
        var x2 = z[1, j].x;
        var y2 = z[1, j].y;
        var x3 = z[2, k].x;
        var y3 = z[2, k].y;
        x2 -= x1;
        y2 -= y1;
        x3 -= x1;
        y3 -= y1;
        return Abs(x2 * y3 - y2 * x3);
    }
    static void getAns((int x, int y)[] a)
    {
        var b = new (int x, int y)[3, 4];
        for (int i = 0; i < 3; i++)
        {
            b[i, 0] = (a[i].x + 1, a[i].y);
            b[i, 1] = (a[i].x, a[i].y + 1);
            b[i, 2] = (a[i].x - 1, a[i].y);
            b[i, 3] = (a[i].x, a[i].y - 1);
        }
        var ans = 0;
        for (int i = 0; i < 4; i++)
            for (int j = 0; j < 4; j++)
                for (int k = 0; k < 4; k++) ans = Max(ans, calc(b, i, j, k));
        Console.WriteLine(ans / 2d);
    }
}