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