using System;

class MainClass
{
	public static void Main (string[] args)
	{
		string str = Console.ReadLine ();
		string[]spStr = str.Split(' ');

		int a = int.Parse (spStr[0]);
		int b = int.Parse (spStr[1]);
		int c = int.Parse (spStr[2]);

		int yakusu = 0;
		for (int i = a; i < b; i++) {
			if (i % c == 0) {
				yakusu++;
			}
		}

		Console.WriteLine (yakusu);


	}
}