using System;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("how many students are going on this trip?");

        int students = int.Parse(Console.ReadLine());

        Console.WriteLine("how many students can fit into one boat?");

        int studentsInBoat = int.Parse(Console.ReadLine());

        Console.WriteLine("how much does it cost to rent one boat?");

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

        double boats = students / studentsInBoat;

        double extraboats = students % studentsInBoat;

        Console.WriteLine("the cost of the trip to a class with {0} students is gonna be {1}.", students, boats*rental + extraboats*rental);

    }

}