#include <iostream>
#include <stdio.h>
#include <math.h>
using namespace std;

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 a=sqrt((double)(x1-x2)*(x1-x2)+(double)(y1-y2)*(y1-y2));
       // cout<<a<<endl;
        double b=sqrt((double)(x1-x3)*(x1-x3)+(double)(y1-y3)*(y1-y3));
        //cout<<b<<endl;
        double c=sqrt((double)(x2-x3)*(x2-x3)+(double)(y2-y3)*(y2-y3));
        //cout<<c<<endl;
        double p=(a+b+c)/2;
        double s=sqrt(p*(p-a)*(p-b)*(p-c));
        printf("%.2lf",s);
        cout<<endl;
    }
    return 0;
}