user input and password

hello

i'm working on this code and it is'nt working properly any help on the codes

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

namespace trial
{
    public class Password
    {
        public static void Main()
        {
            do
            {
                Console.Write("Enter a username:  ");
                string username =Console.ReadLine();

                Console.Write("Enter a password:  ");
                string pass = Console.ReadLine();

                if (username =="john"&& pass=="mjamaa")
                    Console.WriteLine("Login Error");

            }
            while (username =="john"&& pass=="mjamaa");
           
            Console.WriteLine("Login successful");
        }
    }
}