// 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;
        }
        double k = 8.99e9;
        cout << fixed << setprecision(3)
            << k * charge * charge /
(distance * distance);
    }
};
int main() {
    double c, d;
    ElectricCharge e(c, d)
    e.force();
}