double space(double l1,double l2,double l3,double l4,double a)
{
	double l0,pi=3.1415926;
	l0=(l1+l2+l3+l4)/2;
	return (sqrt((l0-l1)*(l0-l2)*(l0-l3)*(l0-l4)-l1*l2*l3*l4*cos(a*pi/360)*cos(a*pi/360)) );
}

int main ( )
{
	double l1,l2,l3,l4,a,l0,pi=3.1415926;
	scanf("%lf\n%lf\n%lf\n%lf\n%lf",&l1,&l2,&l3,&l4,&a);
	l0=(l1+l2+l3+l4)/2;
	if((l0-l1)*(l0-l2)*(l0-l3)*(l0-l4)-l1*l2*l3*l4*cos(a*pi/360)*cos(a*pi/360)>0)
		printf("%.4lf\n",space(l1,l2,l3,l4,a));
	else
		printf("Invalid input\n");
	return 0;
}