Hi,
How can I do this:
-An user download the app and can post a Facebook post in her/him wall and all users that him/her get is more points for him/her in the game. For one user that her/him get = 1 point in the game.
-Only can refferal one time not more. I mean, if user A refferal to user B, user B can’t refferal more times to user A.
How can I do this?
Please suggestions 
Thank you very much in advance!