#include <iostream>
#include<iomanip>

class Electriccharge{
    double q,d;
    public:
    ElectricCharge(double c,double s): q(c),d(s){}
    void show(){
        if(q<=0||d<=0)std::cout<<"Invalid input";
        else std::cout<<std::fixed<<std::setprecision(3)<<8.99e9*q*q/(d*d);
    }
};
int main()
{
    double q,d;
    if(std::cin>>q>>d)ElectricCharge(q,d).show();
    return 0;
}