#include <bits/stdc++.h>
using namespace std;

int main()
{
    double x1,y1,x2,y2,x3,y3;
    cin>>x1>>y1>>x2>>y2>>x3>>y3;
    double a,b,c,ax=x2-x1,ay=y2-y1,bx=x3-x2,by=y3-y2,cx=x1-x3,cy=y1-y3;
    a=sqrt(ax*ax+ay*ay);
    b=sqrt(bx*bx+by*by);
    c=sqrt(cx*cx+cy*cy);
    double p=(a+b+c)/2;
    printf("%.2lf",sqrt(p*(p-a)*(p-b)*(p-c)));
    return 0;
}