// editor1
#include<iostream>
#include<iomanip>
using namespace std;
class ElectricCharge{
    double q,d;
    public:
    ElectricCharge(double d,double q):q(q),d(d) {}
    void force() {
        if (q<=0 || d<=0) {
            cout<<"Invalid input";
            return;
        }
        cout<<fixed<<setprecision(3)<<8.99e9*q*q/(d*d);
    }
};
int main(){
    double q,d;
    cin>>q>>d;
    ELectricCharge e(q,d);
    e.force();
    return 0;
}