#include <stdio.h>
#include <math.h>

int main()
{
	int a[2],b[2],c[2];
	while(scanf("%d %d %d %d %d %d",&a[0],&a[1],&b[0],&b[1],&c[0],&c[1]) != EOF)
	{
		double p,A,B,C;
		double S;
		A = sqrt((fabs(a[0]-b[0]))*(fabs(a[0]-b[0]))+(fabs(a[1]-b[1]))*(fabs(a[1]-b[1])));
		B = sqrt((fabs(a[0]-c[0]))*(fabs(a[0]-c[0]))+(fabs(a[1]-c[1]))*(fabs(a[1]-c[1])));
		C = sqrt((fabs(c[0]-b[0]))*(fabs(c[0]-b[0]))+(fabs(c[1]-b[1]))*(fabs(c[1]-b[1])));
		p = (A+B+C)/2;
		S = sqrt(p*(p-A)*(p-B)*(p-C));
		printf("%.2lf\n",S);
	}
	return 0;
}