#include <bits/stdc++.h>
int main()
{
    double X1,X2,X3,Y1,Y2,Y3,p,a,b,c;
    scanf("%lf%lf%lf%lf%lf%lf",&X1,&X2,&X3,&Y1,&Y2,&Y3);
    
    a=sqrt((X1-X2)*(X1-X2)+(Y1-Y2)*(Y1-Y2));
    b=sqrt((X1-X3)*(X1-X3)+(Y1-Y3)*(Y1-Y3));
    c=sqrt((X2-X3)*(X2-X3)+(Y2-Y3)*(Y2-Y3));
    p=(a+b+c)/2;
    printf("%.2lf\n",sqrt(p*(p-a)*(p-b)*(p-c)));
    return 0;
    
    
    
}