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

double x_1,y_1,x2,y2,x3,y3,a,b,c,p,S;

inline double dis(double x1, double y11, double x2, double y2)
{
    return sqrt((x_1 - x2)*(x_1 - x2)+(y_1 - y2)*(y_1 - y2));
}

int main()
{
    cin>>x_1>>y_1>>x2>>y2>>x3>>y3;
    a=dis(x_1,y_1,x2,y2);
    b=dis(x2,y2,x3,y3);
    c=dis(x3,y3,x_1,y_1);
    p=(a+b+c)/2;
    S=sqrt(p*(p-a)*(p-b)*(p-c));
    printf("%0.2f",S);
    return 0;
}