using System;

public class Program

{

    public static void Main()

    {

    int l,r,k;

        Console.WriteLine("Input :");

        string s = Console.ReadLine();

        string[] values = s.Split(' ');

        l = int.Parse(values[0]);

        r = int.Parse(values[1]);

        k = int.Parse(values[2]);

        int sum=0;

        Console.WriteLine("Output :");

        for(int i = l+1; i < r ; i++){

                if (i%k == 0){

                    sum += i;

                }   

        }

        Console.WriteLine(sum);

    }

}