一本通1034

//qf
#include <bits/stdc++.h>
#define f(i,j,n) for(register int i=j;i<=n;i++)
using namespace std;
typedef long long ll;
inline ll read() {
	ll x=0;
	int f=1;
	char ch=getchar();
	while(!isdigit(ch)) {
		if(ch=='-') f=-1;
		ch=getchar();
	}
	while(isdigit(ch)) x=(x<<1)+(x<<3)+(ch-48),ch=getchar();
	return x*f;
}
inline double dis(double x,double y,double a,double b){
	return sqrt((x-a)*(x-a)+(y-b)*(y-b));
}
double x,x2,x3;
double y,y2,y3;
double a,b,c,area,p;
signed main() {
	cin>>x>>y>>x2>>y2>>x3>>y3;
    a=dis(x,y,x2,y2),b=dis(x,y,x3,y3),c=dis(x2,y2,x3,y3);
	p=(a+b+c)/2.0;
	area=sqrt(p*(p-a)*(p-b)*(p-c));
	cout<<fixed<<setprecision(2)<<area<<endl;
	return 0;
}