using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    private static int number;

    public static void Main()

    {

        var filtered =  Filter();

        filtered.Count();

        filtered.Sum(); 

    }

    private static IEnumerable<int> Filter() 

    { 

        return GetRange()

            .Where(x => {

                if(x % 5 != 0)

                    return false;

                Console.WriteLine("call :" + (++number));

                return true;

            });

    }

    private static IEnumerable<int> GetRange(){ return Enumerable.Range(1,6).ToArray();}

}