10

using System;
using System.Linq;

namespace ExamPreparation
{
    class Startup
    {
        static void Main()
        {
            int[] numbers = Console.ReadLine().Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries)
                .Select(int.Parse)
                .ToArray();
            int diff = int.Parse(Console.ReadLine());
            int found = 0;

            for (int i = 0; i < numbers.Length; i++)
            {
                for (int j = i; j < numbers.Length; j++)
                {
                    if (Math.Abs(numbers[i] - numbers[j]) == diff)
                    {
                        found++;
                    }
                }
            }

            Console.WriteLine(found);
        }
    }
}