题解

#include <iostream>
#include<cstdio>
#include<cmath>
double o;
double func(double a,double b,double c,double d)
{
	o=(a-c)*(b-d)/2;
	if(o<0){
		o=-o;
	}
	return o;
}
using namespace std;
 int main() {
 double x1,y1,x2,y2,x3,y3,p;
 cin>>x1>>y1>>x2>>y2>>x3>>y3;
 p=(max(x1,max(x2,x3)) -min(x1,min(x2,x3)))*(max(y1,max(y2,y3)) -min(y1,min(y2,y3)))-func(x1,y1,x2,y2)-func(x1,y1,x3,y3)-func(x2,y2,x3,y3);
 printf("%0.2lf",p);
}