#include<bits/stdc++.h>
using namespace std;

int main(){
	double x1,x2,x3,y1,y2,y3,a,b,c,s;
	cin>>x1>>y1>>x2>>y2>>x3>>y3;
	a=sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
	b=sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));
	c=sqrt((x2-x3)*(x2-x3)+(y2-y3)*(y2-y3));
	s=(a+b+c)/2;
	int ans=round(sqrt(s*(s-a)*(s-b)*(s-c)));
	cout<<ans<<endl;
	
	return 0;
}