#include <stdio.h>
#include <math.h>

struct pont {
	float x;
	float y;
};

float tav(struct pont P, struct pont Q) {
	return sqrt((P.x-Q.x)*(P.x-Q.x) + (P.y-Q.y)*(P.y-Q.y));
}

int main() {
	struct pont A, B, C;
	float a,b,c,s;
	scanf("%f %f", &A.x, &A.y);
	scanf("%f %f", &B.x, &B.y);
	scanf("%f %f", &C.x, &C.y);
	a=tav(B, C);
	b=tav(A, C);
	c=tav(A, B);
	s=(a+b+c)/2;
	printf("Terulet: %f\n", sqrt(s*(s-a)*(s-b)*(s-c)));
}