How to improve the algorithm?

Question

C++ / C#

There is such a task:

"There are 54 seats in a reserved seat car, which are located in nine compartments. Seats from 1 to 36 are basic and they are located four in a compartment (1 - 4 in the first, ..., 33 - 36 in the ninth), from 37 up to 54 - side, divided into two, but the location of the compartment is reversed: places 37, 38 are in the ninth compartment, 39 and 40 in the eighth, ..., 53 and 54 in the first. Determine the compartment number by the seat number.

I solved it like this:

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

namespace ConsoleApp1
{
    class Program
    {
        private static int _placesCount;
        private static int _roomCount = 18;

        private static int _mainRoomPlacesCount = 4;
        private static int _sideRoomPlacesCount = 2;

        static void Main(string[] args)
        {
            _placesCount = (_roomCount / 2 * _mainRoomPlacesCount) + (_roomCount / 2 * _sideRoomPlacesCount);

            while(true)
            {
                var number = 0;

                Console.WriteLine("\n\nВведите номер места:");

                var ParceResult = int.TryParse(Console.ReadLine(), out number);

                if (ParceResult)
                {
                    if(number <= _placesCount && number > 0)
                    {
                        var result = FindRoomByPlace(number);

                        Console.WriteLine("Вывод: " + result);
                    }
                    else
                    {
                        Console.WriteLine("Такого места не существует!");
                    }
                }
                else
                {
                    Console.WriteLine("Ошибка. Не удалось преобразовать строку в число.");
                }
            }
        }

        private static double FindRoomByPlace(int placeNumber)
        {
            var mainPlacesCount = _roomCount / 2 * _mainRoomPlacesCount;

            if(placeNumber <= mainPlacesCount)
            {
                return Math.Ceiling((double)placeNumber / _mainRoomPlacesCount);
            }
            else
            {
                return Math.Ceiling((double)(_placesCount - placeNumber + 0.5f) / _sideRoomPlacesCount);
            }
        }
    }
}

Is there any better option?

Answer 1

if (n < 37)
  return (int)((n-1) >> 2)+1;
else
  return (int)((54-n+1) >> 1)+1;

Something like this
Why is your FindRoomByPlace double?
Are there fractional compartments?
What is RoomCount and why are there 18 of them?
The code is disgusting