#include<iostream>
#include<iomanip>
using namespace std;
class charge{
    double q,d;
    public:
    charge(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)charge(q,d).show();
    return 0;
}