#include<bits/stdc++.h>
using namespace std;
int main(){
	int a1,a2,b1,b2,c1,c2;
	cin>>a1>>a2>>b1>>b2>>c1>>c2;
	double ab,bc,ac,s,ans;
	ab=sqrt((a1-a2)*(a1-a2)+(b1-b2)*(b1-b2));
	bc=sqrt((b1-b2)*(b1-b2)+(c1-c2)*(c1-c2));
	ac=sqrt((a1-a2)*(a1-a2)+(c1-c2)*(c1-c2));
	s=(ab+ac+bc)/2;
	ans=sqrt(s*(s-ab)*(s-bc)*(s-ac));
	cout<<fixed<<setprecision(0)<<ans;
    return 0;
}