чебоксары

#include <bits/stdc++.h>
using namespace std;
int main()
{
	freopen("trianglearea.in","r", stdin);
	freopen("trianglearea.out","w", stdout);
	double x,y,a,b,c,x1,x2,y1,y2,p;
	cin >> x >> y >> x1 >> y1 >> x2 >> y2;
	a = sqrt(((x-x1)*(x-x1))+((y-y1)*(y-y1)));
	b = sqrt(((x1-x2)*(x1-x2))+((y1-y2)*(y1-y2)));
	c = sqrt(((x2-x)*(x2-x))+((y2-y)*(y2-y)));
	p = (a+b+c)/2;
	if ((a+b<=c)||(c+b<=a)||(c+a<=b)) cout << -1;
	else {
		p = sqrt(p*(p-a)*(p-b)*(p-c));
		cout << fixed << setprecision(12) << p;
	}
}