using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var projectIdsToExclude = new List<int>{1,3,5};

        var allProjectIds = new List<int>{1,2,3,4,5,6,7};

        var filteredList = allProjectIds.Where(a => !projectIdsToExclude.Contains(a));

        foreach(var item in filteredList)

            Console.Write(item);

    }

}