AdalServiceException: Response status code does not indicate success: 406 (NotAcceptable)

Question

I am getting the following type of error:

AdalServiceException: Response status code does not indicate success: 406 (NotAcceptable)

The code is for generating barier token for Azure Active Directory authentication based on a user name and password.

Also, what do I put in these variables, especially resource?

This is my code (.NET Core console application)

static void Main(string[] args)
    {
        Console.WriteLine(GetToken());
        Console.ReadLine();
    }

    public static string tenantId = "********************************";
    public static string clientId = "*******************************";
    public static string resource = "(What to put in this)";
    public static string username = "**************";
    public static string password = "***********************";

    public static string GetToken()
    {
      
        var upc = new UserPasswordCredential(username, password);
        var context = new AuthenticationContext("https://login.microsoftonline.com/" + tenantId);
        AuthenticationResult result = context.AcquireTokenAsync(resource, clientId, upc).Result;
        return result.AccessToken;

    }