variable scope

i don't know were im getting wrong. challenge task 1 0f 1 compiling the below code currently produces the error: " the name 'output' does not exist in the c The output variable is declared twice: once within the if statement's curly braces and again within . The last line of code in this program, console.writeLine(output);, is attempting to use a variable named output, which doesn't exist outside of the if/else statement's curly braces. To fix this error: Declare the output variable just before the if statement and assign it to an empty string (i.e"") Remove the string data types from the output variables within the if/else statement's curly braces.

program.cs

using System;

namespace Treehouse.CodeChallenges
{
    class Program
    {
        static void Main()
        {            
           input = Console.ReadLine();

            output = Console.WriteLine();
            if (input =="quit")
            {
              string output = "";
            }
            else
            {
               string output = +input + ;
            }

            Console.WriteLine(output);
        }
    }
}