for PHP-man

train.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace TrainSelector
{
    class Program
    {
        static void Main(string[] args)
        {
            var seatToCoupes = new Dictionary<Int32, Int32>();
            var mainCoupeSize = 4;
            var leftCoupeSize = 2;
            var coupeCount = 9;
            var totalMainSeatsOffset = coupeCount * mainCoupeSize;

            for (var currentCoupe = 1; currentCoupe <= coupeCount; currentCoupe++)
            {
                for (var offsetMainSeatNumber = 1; offsetMainSeatNumber <= mainCoupeSize; offsetMainSeatNumber++)
                {
                    var currentMainSeatNumber = (currentCoupe - 1) * mainCoupeSize + offsetMainSeatNumber;
                    seatToCoupes.Add(currentMainSeatNumber, currentCoupe);
                }

                for (var offsetLeftSeatNumber = 1; offsetLeftSeatNumber <= leftCoupeSize; offsetLeftSeatNumber++)
                {
                    var currentLeftSeatNumber = (coupeCount - currentCoupe) * leftCoupeSize + offsetLeftSeatNumber + totalMainSeatsOffset;
                    seatToCoupes.Add(currentLeftSeatNumber, currentCoupe);
                }
            }

            Console.WriteLine(seatToCoupes[54]);

        }
    }
}