Currency Convertor C#

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

namespace Program
{
    class Program
    {
        static void Main()
        {
          var value = double.Parse(Console.ReadLine());
          var input = Console.ReadLine();// Enter BGN, USD, EUR or GBP currency
            var output = Console.ReadLine();// Enter BGN, USD, EUR or GBP currency

            var bgn = 1.0;
            var usd = 1.79549;
            var eur = 1.95583;
            var gbp = 2.53405;
            switch (input)
            {
                case "BGN":
                    break;
                case "USD":
                    value = value * usd;
                    break;
                case "EUR":
                    value = value * eur;
                    break;
                case "GBP":
                    value = value * gbp;
                    break;
                default:
                    break;
            }
            switch (output)
            {
                case "BGN":
                    value = value / bgn;
                    break;
                case "USD":
                    value = value / usd;
                    break;
                case "EUR":
                    value = value / eur;
                    break;
                case "GBP":
                    value = value / gbp;
                    break;
                default:
                    break;
            }
            Console.WriteLine(Math.Round(value, 2) + " " + output);
        }
    }
}