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