mu 1 2 3
mu 3 2 4
mu 3 4 5
mu 3 5 6
mu 6 3 7
mu 2 7 8
mu 3 7 9
mu 6 7 10
mu 1 10 11
mu 10 3 12
mu 11 4 13
mu 4 9 14
mu 14 8 15
oup 10 12 11 7 6 13 8 15 9 10 3
echo "classes  6C  6D  7A  8A  8B  9A  9C 12A 12B 13A"