int main(int argc, char* argv[])
{   
    double S,s,a,b,c,d,e;
    double f;
    scanf ("%lf %lf %lf %lf %lf",&a,&b,&c,&d,&e);
    s = (a+b+c+d)/2;
    f=(s-a)*(s-b)*(s-c)*(s-d)-a*b*c*d*cos(e/2*(3.1415926/180))*cos(e/2*(3.1415926/180));
    S = sqrt(f);
	if (f<0){  
    printf("Invalid input");
                  } 
	else {
		printf("%.4lf",S);
                }
	return 0;
}
