#include 
#include 
using namespace std;
int main()
{
//(|x|-|y|)/(1+|xy|)
float x,y;
cin >> x >> y;
cout.setf(ios::fixed|ios::showpoint);
cout.precision(1);
cout << (abs(x)-abs(y))/((1+abs(x*y)));
return 0;
}