using System;

namespace No048_ロボットの操縦
{
    class Program
    {
        static void Main(string[] args)
        {            int x = int.Parse(Console.ReadLine());
            int y = int.Parse(Console.ReadLine());
            int l = int.Parse(Console.ReadLine());
            int count = 0;

            if (y < 0)
            {
                if (x < 0)
                    count += 2;
                else if (x == 0)
                    count += 2;
                else
                    count += 2;
            }
            else
            {
                if (x < 0)
                    count++;
                else if (x == 0)
                    count += 0;
                else
                    count++;
            }

            x = Math.Abs(x);
            y = Math.Abs(y);

            count += Floor(x, l);
            count += Floor(y, l);

            Console.WriteLine(count);
        }

        static int Floor(int a, int b)
        {
            int result;

            for (result = 0; result * b < a; result++) ;

            return result;
        }
    }
}