Know nothing about Yam, but that he has a cool name and is from Isreal. I'm sure this is a stash pick, so don't expect to see him fighting for a spot on the Celtics for at least a year.
Will watch these videos now and learn about Madar in real time:
UPDATE: 12:05 AM Already like him! Hopefully he becomes one of the international stash 2nd rounders that every team, but the Celtics (So far!) seem to strike gold with from time to time.