#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::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;
}