using System;

using System.Linq;

using System.Collections;

using System.Collections.Immutable;

public class Program

{

    public static void Main()

    {

        var input = "2333133121414131402";

        var lastFileId = 0;

        var map = input

            .Select((c, i) => {

                if (i % 2 == 0) {

                    return new string(

                        string.Join("",

                            (lastFileId++)

                                    .ToString()

                                    .Select(x => Convert.ToChar(x.ToString()))

                                    ,int.Parse(input[i].ToString());

                }

                else {

                    return new string('.', int.Parse(input[i].ToString();

                }

            })

            .Aggregate((sum, s) => sum + s);

        Console.WriteLine(map);

        // Build an ordered list of position where free space is available

        var freeBlockSpaceIndices = new Queue(map

            .Select((x, i) => x == '.' ? i : -1)

            .Where(index => index >= 0).ToList());

        //Console.WriteLine(string.Join(",", freeBlockSpaceIndices));

        var mapArray = map.ToList();

        for (var j = map.Length-1; j >= 0; j--)

        {

            if (mapArray[j] != '.')

            {

                var space = int.Parse(freeBlockSpaceIndices.Dequeue().ToString());

                mapArray[space] = mapArray[j];

                mapArray[j] = '.';

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

​

                // Exit when all dots continuous

                if (mapArray.Skip(mapArray.IndexOf('.')).All(c => c == '.'))

                    break;

            }       

        }

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

        var i = 0;

        var checksum = mapArray.Where(c => c != '.').Sum(c => int.Parse(c.ToString()) * i++);

        Console.WriteLine(checksum);

    }

}