import java.util.*;
 
public class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
		Scanner in = new Scanner(System.in);
		double
			Ax = in.nextDouble(),
			Ay = in.nextDouble(),
			Az = in.nextDouble(),
			Bx = in.nextDouble(),
			By = in.nextDouble(),
			Bz = in.nextDouble(),
			Cx = in.nextDouble(),
			Cy = in.nextDouble(),
			Cz = in.nextDouble();
		double V = (Ax * (By * Cz - Bz * Cy) - Bx * (Ay * Cz - Az * Cy) + Cx * (Ay * Bz - Az * By)) / 6.0;
		if (V < 0) V *= -1;
		System.out.print(V);
	}
}

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MCAwIDEKMCAxIDAKMSAwIDA=

0 0 1
0 1 0
1 0 0