#include <cstdio>

 #include <cstring>

 #include <cmath>

 #include <algorithm>

 using namespace std;

 const double eps=1e-;

 double getarea(double a,double b,double c)

 {

     double p=(a+b+c)/2.0;

     return (c*c/+sqrt(p*(p-a)*(p-b)*(p-c)));

 }

 int main()

 {

     double x,y;

     scanf("%lf%lf",&x,&y);

     double l=x+y,r=sqrt(x*x+y*y),s1;

     while(fabs(r-l)>eps)

     {

         double mid1=(r+l)/;

         double mid2=(mid1+l)/;

         s1=getarea(x,y,mid1);

         double s2=getarea(x,y,mid2);

         if(s1>s2)

         l=mid2;

         else

         r=mid1;

     }

     printf("%.9lf\n",s1);

     return ;

 }