#include<cstdio>
#include<iostream>
#include<string>
#include<map>
#include<cmath>
using namespace std;

double SideLength(int x1,int y1,int x2,int y2){
    int a = abs(x1 - x2);
    int b = abs(y1 - y2);
    return sqrt(pow(a,2)+pow(b,2));
}

int main(){

    int x1,y1,x2,y2,x3,y3;
    while(scanf("%d%d%d%d%d%d",&x1,&y1,&x2,&y2,&x3,&y3) != EOF){

       double len1 = SideLength(x1,y1,x2,y2);
        double len2 = SideLength(x1,y1,x3,y3);
        double len3 = SideLength(x2,y2,x3,y3);

       double p = (len1 + len2 + len3) / 2;//周长的一半

       double area = sqrt(p*(p-len1)*(p-len2)*(p-len3));//海伦公式

       printf("%.2lf\n",area);
//       cout << area << endl;
    }
}