import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int[] x = new int[3];
		int[] y = new int[3];
		for (int i = 0; i < 3; i++) {
			x[i] = sc.nextInt();
			y[i] = sc.nextInt();
		}
		sc.close();

		int[] dx = {1, 0, -1, 0};
		int[] dy = {0, 1, 0, -1};
		int max = 0;
		for (int i = 0; i < 4; i++) {
			int x1 = x[0] + dx[i];
			int y1 = y[0] + dy[i];
			for (int j = 0; j < 4; j++) {
				int x2 = x[1] + dx[j];
				int y2 = y[1] + dy[j];
				for (int k = 0; k < 4; k++) {
					int x3 = x[2] + dx[k];
					int y3 = y[2] + dy[k];
					int s = x1 * y2 + x2 * y3 + x3 * y1 - y1 * x2 - y2 * x3 - y3 * x1;
					int s2 = Math.abs(s);
					max = Math.max(max, s2);
				}
			}
		}
		System.out.println(max / 2.0);
	}
}