Recursively get last record from same table parent child

I want to get last reference Id from same table. I have following table.

 ID   UserId   DelegatedToUserId
 1      100       101
 2      101       102
 3      102       103
 4      103       NULL
 5      104       109

I just can't get my head around. I know what I want, just simply can't get it out on the screen. So when I ask for 100 query should return 103, when I ask 101 or 102 again it should return 103. when user enters 104 it should return 109

And when I ask for 103 it should return 103 as there is no delegate for this.

can this be done in single sql query ?

Personally, I would go with this:

DECLARE @UserID int = 103;

WITH VTE AS
    (SELECT *
     FROM (VALUES (1, 100, 101),
                  (2, 101, 102),
                  (3, 102, 103),
                  (4, 103, NULL),
                  (5, 104, 109)) AS V (ID, UserID, DelegatedToUserID) ),
rCTE AS
    (SELECT V.ID,
            V.UserID,
            V.DelegatedToUserID
     FROM VTE V
     WHERE UserID = @UserID
     UNION ALL
     SELECT V.ID,
            V.UserID,
            V.DelegatedToUserID
     FROM rCTE r
          JOIN VTE V ON r.DelegatedToUserID = V.UserID)
SELECT *
FROM rCTE
WHERE rCTE.DelegatedToUserID IS NULL;

As I mentioned in the comments, however, passing 104 will return no rows as user 109 does not exist in the table.