#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;
}