Currency Converter

    using System;

    class Currency_Converter
    {
        static void Main(string[] args)
        {
            // 1BGN=1.79549 USD;
            // 1BGN=1.95583 EUR;
            // 1BGN=2.53405 GBP;
            decimal inputValue = decimal.Parse(Console.ReadLine());

            decimal oneGBP = 1 / 2.53405M;
            decimal oneEUR = 1 / 1.95583M;
            decimal d = oneEUR / oneGBP;
            decimal oneUSD = 1 / 1.79549M;
            decimal d1 = oneUSD / oneEUR;

            decimal oneUSDToGBP = 2.53405M/1.79549M;
            decimal oneEURToBGN = 1 / 1.95583M;
            decimal oneEURToUSD = 1.79549M / 1.95583M;
            decimal oneEURtoGBP = 1.95583M/2.53405M;

            decimal oneGBPToBGN = 1 / 2.53405M;
            //OK
            decimal oneGBPtoEUR = 2.53405M / 1.95583M;
            decimal oneGBPtoUSD = 2.53405M / 1.79549M;

            string value1 = Console.ReadLine();
            string value2 = Console.ReadLine();

            if (value1=="BGN" && value2=="USD")
            {
                Console.WriteLine("{0:F2} USD", inputValue * 1.79549M);
            }
            else if (value1 == "BGN" && value2 == "EUR")
            {
                Console.WriteLine("{0:F2} EUR", inputValue / 1.95583M);
            }
            else if (value1 == "BGN" && value2 == "GBP")
            {
                Console.WriteLine("{0:F2} GBP", inputValue * 2.53405M);
            }


            //OK
            else if (value1 == "USD" && value2 == "BGN")
            {
                Console.WriteLine("{0:F2} BGN", inputValue *1.79549M);
            }
            //Ok
            else if (value1 == "USD" && value2 == "EUR")
            {
                Console.WriteLine("{0:F2} EUR", inputValue / d1);
            }

            //OK
            else if (value1 == "USD" && value2 == "GBP")
            {
                Console.WriteLine("{0:F2} GBP", inputValue * oneUSDToGBP);
            }


            //OK
            else if (value1 == "EUR" && value2 == "BGN")
            {
                Console.WriteLine("{0:F2} BGN", inputValue * oneEURToBGN);
            }

            //OK
            else if (value1 == "EUR" && value2 == "USD")
            {
                Console.WriteLine("{0:F2} USD", inputValue * oneEURToUSD);
            }


            //OK
            else if (value1 == "EUR" && value2 == "GBP")
            {
                Console.WriteLine("{0:F2} GBP", inputValue * oneEURtoGBP);
            }


            //OK
            else if (value1 == "GBP" && value2 == "BGN")
            {
                Console.WriteLine("{0:F2} BGN", inputValue * oneGBPToBGN);
            }

            //OK
            else if (value1 == "GBP" && value2 == "EUR")
            {
                Console.WriteLine("{0:F2} EUR", inputValue * oneGBPtoEUR);
            }
            //OK
            else if (value1 == "GBP" && value2 == "USD")
            {
                Console.WriteLine("{0:F2} USD", inputValue * oneGBPtoUSD);
            }
        }
    }