using System;

public class Program

{

    public static void Main()

    {

        int N, M, K;

        N= Convert.ToInt16(Console.ReadLine());

        M= Convert.ToInt16(Console.ReadLine());

        K= Convert.ToInt16(Console.ReadLine());

​

        int r = (N+M)/K;

        if((N+M)% K > 0){

            r += 1;

            Console.WriteLine(r);

            return;

        }

        if(N <= 10000 && M <= 10000 && K <= 10000){

            if(r==0)

            {

                Console.WriteLine("0");

                return;

            }

            else{

                int i = r*2;

                if(M <= i){

                    Console.WriteLine("0");

                    return;

                }

                else{

                    Console.WriteLine(r);

                    return;

                }

            }

        }

    }

}