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

using System.Text;
using System.Threading.Tasks;

namespace Exercice
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] values = Console.ReadLine().Split().Select(int.Parse).ToArray();

            int diff = int.Parse(Console.ReadLine());

            int counter = 0;
            bool pairs = false;

            for (int i = 0; i < values.Length; i++)
            {
                for (int j = i; j < values.Length; j++)
                {
                    if (Math.Abs(values[i]-values[j]) == diff)
                    {
                        counter++;
                        pairs = true;
                    }
                }
            }

            if (!pairs)
            {
                Console.Write("0");
            }
            else
            {
                Console.Write(counter);
            }


        }
    }
}