Stuck_Zipper_50%

using System;
using System.Collections.Generic;
using System.Linq;

namespace Stuck_Zipper
{
    class Program
    {
        static void Main(string[] args)
        {
            List<int> first = Console.ReadLine().Split(' ').Select(int.Parse).ToList();

            List<int> second = Console.ReadLine().Split(' ').Select(int.Parse).ToList();

            List<int> firstIndex = new List<int>();
            List<int> secondIndex = new List<int>();

            for (int i = 0; i < first.Count; i++)
            {
                secondIndex.Add(first[i]);

                for (int j = secondIndex.Count - 1; j >= 0; j--)
                {
                    if (Math.Abs(first[i]).ToString().Length > Math.Abs(secondIndex[j]).ToString().Length)
                    {
                        secondIndex.Remove(first[i]);
                    }
                    else if (Math.Abs(first[i]).ToString().Length < Math.Abs(secondIndex[j]).ToString().Length)
                    {
                        secondIndex.Remove(secondIndex[j]);
                    }
                }
            }

            for (int i = 0; i < second.Count; i++)
            {
                firstIndex.Add(second[i]);

                for (int j = firstIndex.Count - 1; j >= 0; j--)
                {
                    if (Math.Abs(second[i]).ToString().Length > Math.Abs(firstIndex[j]).ToString().Length)
                    {
                        firstIndex.Remove(second[i]);
                    }
                    else if (Math.Abs(second[i]).ToString().Length < Math.Abs(firstIndex[j]).ToString().Length)
                    {
                        firstIndex.Remove(firstIndex[j]);
                    }
                }
            }

            for (int i = 0; i < firstIndex.Count; i++)
            {
                for (int j = 0; j < secondIndex.Count; j++)
                {
                    if (Math.Abs(firstIndex[i]).ToString().Length > Math.Abs(secondIndex[i]).ToString().Length)
                    {
                        firstIndex.Remove(firstIndex[i]);
                    }
                    else if (Math.Abs(secondIndex[i]).ToString().Length > Math.Abs(firstIndex[i]).ToString().Length)
                    {
                        secondIndex.Remove(secondIndex[i]);
                    }
                }
            }

            int maxCount = Math.Max(firstIndex.Count, secondIndex.Count);

            List<int> zipped = new List<int>();

            for (int i = 0; i <= maxCount; i++)
            {
                if (i < firstIndex.Count)
                {
                    zipped.Add(firstIndex[i]);
                }
                if (i < secondIndex.Count)
                {
                    zipped.Add(secondIndex[i]);
                }
            }
            Console.WriteLine(string.Join(" ", zipped));
        }
    }
}