#include <stdio.h>

int main(){
	double x1,y1,x2,y2,x3,y3;
	while(scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3)!=EOF){
		double a=sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
		double b=sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));
		double c=sqrt((x2-x3)*(x2-x3)+(y2-y3)*(y2-y3));
		double p=(a+b+c)/2;
		double s=sqrt(p*(p-a)*(p-b)*(p-c));
		printf("%.2lf\n",s);
	}
	return 0;
}