#include<stdio.h>
#include<math.h> 

double calculateArea(double x1,double y1,double x2,double y2,double x3,double y3){
    return fabs((x1*(y2 - y3) + x2*(y3 -y1) + x3*(y1 - y2))/2.0);
    //fabs确保为正数 
}

int main(){
    double x1,y1,x2,y2,x3,y3;
    while(scanf("%lf %lf %lf %lf %lf %lf",&x1,&y1,&x2,&y2,&x3,&y3) != EOF){
        double area = calculateArea(x1,y1,x2,y2,x3,y3);
        printf("%.2f\n",area);
    }
    return 0;
}