Pairs_by_Difference

using System;

using System.Linq;

namespace Pairs_by_Difference
{
    class Pairs_by_Difference
    {
        static void Main(string[] args)
        {
            int[] array = Console.ReadLine().Split().Select(int.Parse).ToArray();
            int difference = int.Parse(Console.ReadLine());
            int count = 0;
            for (int i = 0; i < array.Length; i++)
            {
                for (int j = 1; j < array.Length; j++)
                {
                    if (array[j] - array[i] == difference)
                    {
                        count++;
                    }
                }
            }
            Console.WriteLine(count);
        }
    }
}