What's the prob with it? : I am getting error "use of unassigned variable ch" at while(ch != 'n').
I am using visual studio 2015



namespace ConsoleApplication2
{
    class Program
    {
        
        static void Main(string[] args)
        {
            char ch;
            do
            {
                Console.WriteLine("Enter any number");
                int i = Convert.ToInt32(Console.ReadLine());
                for (int j = 1; j <= 200; j++)
                {
                    int c = i * j;
                    Console.Write("  " + c);
                    if (j % 10 == 0)
                    {
                        Console.WriteLine();
                    }
                    Console.WriteLine("again? " + "(y//n)");
                    ch = Convert.ToChar(Console.ReadLine());
                    if (ch == 'y' || ch == 'n')
                        continue;
                    else
                    {
                        Console.WriteLine("invalid choice");
                        break;
                    }
                }
            }while (ch != 'n');
            }

            }
    }