Jonathan has a magical coin machine which takes coins in amounts of 7,8, and 9 . If he puts in 7 coins, he gets 3 coins back; if he puts in 8, he gets 11 back; and if he puts in 9, he gets 4 back. The coin machine does not allow two entries of the same amount to happen consecutively. Starting with 15 coins, what is the minimum number of entries he can make to end up with 4 coins?