chor 1 3
chor 2 5
mu 1 2 3
chor 3 7
iv 2 4
mu 1 4 5  # ab^-1
chor 5 7
iv 1 8
mu 8 2 9  # a^-1b
mu 3 9 10
mu 10 2 11
mu 11 3 12
mu 12 9 13
mu 13 3 14
mu 14 2 15
mu 15 9 16
chor 16 1