using System;

public class Program

{

    public static void Main()

    {

        double m1,m2,r,F,G;

        Console.Write("la masse de la premiere planette: ");

        m1 = double.Parse(Console.ReadLine());

        Console.Write("la masse de la deuxieme planette: ");

        m2 = double.Parse(Console.ReadLine());

        Console.Write("la distance entre les 2 planettes: ");

        r = double.Parse(Console.ReadLine());

        G=(6.673*10e-11)/1000;

        F=G*m1*m2/r*r;

        Console.Write("F :" +F);    

    }   

}