#include<iostream>
#include<cmath>
using namespace std;
double dis(double x1,double y1,double x2,double y2){
    return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
}/*求两点距离*/
double answer(double a,double b,double c){
    double p=(a+b+c)/2;
    return sqrt(p*(p-a)*(p-b)*(p-c));
}/*海伦-秦九韶公式求面积*/
int main(){
    double x1,y1,x2,y2,x3,y3;/*三点坐标*/
	cin>>x1>>y1>>x2>>y2>>x3>>y3;
    int a=dis(x1,y1,x2,y2);
    int b=dis(x1,y1,x3,y3);
    int c=dis(x2,y2,x3,y3);/*三边距离*/
	printf("%.3f",answer(a,b,c));/*保留小数*/
	return 0;
}

直接送走