using System;
using System.Collections.Generic;
using System.Linq;

// No.810 割った余りの個数
namespace No._810
{
    class Program
    {
        static void Main(string[] args)
        {
            int L, R, M;
            int[] p = Array.ConvertAll(Console.ReadLine().Split(' '), int.Parse);
            L = p[0];
            R = p[1];
            M = p[2];

            var dic = new Dictionary<int, int>();
            int div;
            for (int i = L; i <= R; i++)
            {
                div = i % M;
                if (!dic.ContainsKey(div))
                {
                    dic.Add(div, 0);
                }
            }

            Console.WriteLine(dic.Count());
        }
    }
}