#include<bits/stdc++.h>
using namespace std;
int main()
{
    double x1,x2,x3,y1,y2,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((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));
        double p=((a+b+c)/2.0);
        double s=sqrt(p*(p-a)*(p-b)*(p-c));
        printf("%.2lf\n",s);
    }
    return 0;
 }