#include<iostream>
#include<iomanip>

class ElectricCharge{
    double q,d;
    ElectricCharge(double c,double s):q(c),d(s){
        viod 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;
    }
}