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