using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public void Main()

    {

        var l2 = new List<int>{1,3,2,3,4,5};

        var l1 = new List<int>{11,33};

        var res = MergeListStagger<int>(l1,l2,120);

        Console.WriteLine(string.Join(",",res));

    }

     public List<T> MergeListStagger<T>(List<T> list1, List<T> list2 , int num = 1)

        {

            var res = new List<T>();

            var Size = Math.Min(list1.Count, list2.Count);

            int i = 0;

            while (i <= Size)

            {

                var i1 = i;

                for (int n = 0; n < num && i + n < Size; n++)

                {

                    res.Add(list1[i + n]);

                }

                for (int n = 0; n < num && i + n < Size; n++)

                {

                    res.Add(list2[i + n]);

                }

                i = Math.Min(i + num - 1, Size) + 1;

            }

            if (list1.Count > list2.Count)

            {

                res.AddRange(list1.Skip(Size));

            }

            else if (list1.Count < list2.Count)

            {

                res.AddRange(list2.Skip(Size));

            }

​

            return res;

        }

}