int main()
{   double PI;
	double a,b,c,d;
	double f,e;
	double s,S;
         PI=3.1415926;
	scanf("%lf%lf%lf%lf", &a, &b, &c, &d);
	scanf("%lf", &f);
	e = f*2*PI/360;
         s = (a+b+c+d)/2;
	S = sqrt((s-a)*(s-b)*(s-c)*(s-d) - a*b*c*d*cos(e/2)*cos(e/2));
	if ((s-a)*(s-b)*(s-c)*(s-d) - a*b*c*d*cos(e/2)*cos(e/2)>=0){
		printf("%.4lf", S);
	}
	else printf("Invalid input");
	return 0;
}