using System;

using System.Linq;

using System.Collections.Generic;

​

public class HowManyNumbers

{

    public static void Main()

    {

        Console.WriteLine(SelNumber(100, 3));

    }

​

    public static int SelNumber(int n, int d)

    {

        if (n < 12) return 0;

        return Enumerable.Range(12, n - 12 + 1) //12..n-12+1

            .Where(i => 

                   GetReversedDigits(i).Zip(    //Zip allows to compare 2 lists element by element

                       GetReversedDigits(i).Skip(1).Concat(new[]{0}), 

                       (x, y) => x - y)

                   .Take(i.ToString().Length - 1)

                   .All(x => x > 0 && x <= d))  //condition is TRUE is all elements are satisfied

            .Count();

    }

​

    public static IEnumerable<int> GetReversedDigits(int i)

    {

        return i.ToString().Reverse().Select(x => x - '0');

    }

}