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

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)

        {
            List<int> numbers = Console.ReadLine().Split().Select(int.Parse).ToList();
            int diff = int.Parse(Console.ReadLine());
            int k = 0;

            for (int i = 0; i < numbers.Count - 1; i++)
            {
                for (int n = i + 1; n < numbers.Count; n++)
                {
                    if (Math.Abs(numbers[i] - numbers[n]) == diff)
                    {
                        k += 1;
                    }
                }
            }

            Console.WriteLine(k);
        }
    }
}