(VAR)
(RULES
c0 -> c6
c0 -> c13
c6 -> c7
c13 -> c14
c1 -> c7
c1 -> c14
c7 -> c8
c14 -> c15
c2 -> c8
c2 -> c15
c8 -> c9
c15 -> c16
c3 -> c9
c3 -> c16
c9 -> c10
c16 -> c17
c4 -> c10
c4 -> c17
c10 -> c11
c17 -> c18
c5 -> c11
c5 -> c18
c11 -> c12
c18 -> c12
c12 -> c6
c12 -> c13
)