Conditional Statements - Sign Of Product

using System;

    class SignOfProduct
    {
        static void Main(string[] args)
        {


            decimal enteredNumber;
            bool successParse;
            bool isZero = false;
            byte counter = 0;

            for (int i = 0; i < 3; i++)
            {
                do
                {
                    Console.Write("Enter the {0} number: ", i+1);
                    successParse = decimal.TryParse(Console.ReadLine(), out enteredNumber);

                } while (!successParse);

                if (enteredNumber<0)
                {
                    counter++;
                }

                else if (enteredNumber==0)
                {
                    Console.WriteLine("The product is ZERO");
                    isZero = true;
                    break;
                }
            }

            if (!isZero)
            {

                if (counter % 2 == 0)
                {
                    Console.WriteLine("The sign is +");
                }

                else
                {
                    Console.WriteLine("The sign is -");
                }
            }




        }

    }