16
(A(B((I(CED))((((GH)J)F)((K(MN))(L(OP)))))))
A tar rec
B rec rec
C pia rec
D rec rec
E tor rec
F gel rec
G tar rec
H rec rec
I rec rec
J tor rec
K tar rec
L tar rec
M tar rec
N rec rec
O tar rec
P rec rec