import java.io.*;
import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        Point[] points = new Point[3];
        for (int i = 0; i < 3; i++) {
            points[i] = new Point(sc.nextInt(), sc.nextInt());
        }
        Point[] pattern = new Point[]{new Point(1, 0), new Point(-1, 0), new Point(0, 1), new Point(0, -1)};
        double ans = 0;
        for (int i = 0; i < 4; i++) {
            points[0].add(pattern[i]);
            for (int j = 0; j < 4; j++) {
                points[1].add(pattern[j]);
                for (int k = 0; k < 4; k++) {
                    points[2].add(pattern[k]);
                    ans = Math.max(ans, points[0].getSpace(points[1], points[2]));
                    points[2].draw(pattern[k]);
                }
                points[1].draw(pattern[j]);
            }
            points[0].draw(pattern[i]);
        }
        System.out.println(ans);
    }
    
    static class Point {
        double x;
        double y;
        
        public Point(double x, double y) {
            this.x = x;
            this.y = y;
        }
        
        public void add(Point p) {
            x += p.x;
            y += p.y;
        }
        
        public void draw(Point p) {
            x -= p.x;
            y -= p.y;
        }
        
        public double getSpace(Point p1, Point p2) {
            double ans = (p1.x - x) * (p2.y - y) - (p1.y - y) * (p2.x - x);
            return Math.abs(ans) / 2;
        }
    }
}
class Scanner {
    BufferedReader br;
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() {
        try {
            br = new BufferedReader(new InputStreamReader(System.in));
        } catch (Exception e) {
            
        }
    }
    
    public int nextInt() {
        return Integer.parseInt(next());
    }
    
    public long nextLong() {
        return Long.parseLong(next());
    }
    
    public double nextDouble() {
        return Double.parseDouble(next());
    }
    
    public String next() {
        try {
            while (!st.hasMoreTokens()) {
                st = new StringTokenizer(br.readLine());
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            return st.nextToken();
        }
    }
    
}