---- CR(R)
---- [van Oostrom, RTA 2008].
R:
a1() -> b1()
a1() -> c1()
b1() -> b2()
c1() -> c2()
a2() -> b2()
a2() -> c2()
b2() -> b3()
c2() -> c3()
a3() -> b3()
a3() -> c3()
b3() -> b4()
c3() -> c4()
a4() -> b4()
a4() -> c4()
b4() -> b5()
c4() -> c5()
a5() -> b5()
a5() -> c5()
b5() -> b6()
c5() -> c6()
a6() -> b6()
a6() -> c6()
b6() -> b7()
c6() -> b7()
b7() -> b1()
b7() -> c1()

Label:
[a1() -> b1()] = 5
[a1() -> c1()] = 1
[b1() -> b2()] = 0
[c1() -> c2()] = 0
[a2() -> b2()] = 1
[a2() -> c2()] = 1
[b2() -> b3()] = 0
[c2() -> c3()] = 0
[a3() -> b3()] = 11
[a3() -> c3()] = 3
[b3() -> b4()] = 0
[c3() -> c4()] = 0
[a4() -> b4()] = 15
[a4() -> c4()] = 3
[b4() -> b5()] = 0
[c4() -> c5()] = 0
[a5() -> b5()] = 14
[a5() -> c5()] = 15
[b5() -> b6()] = 0
[c5() -> c6()] = 0
[a6() -> b6()] = 1
[a6() -> c6()] = 13
[b6() -> b7()] = 0
[c6() -> b7()] = 0
[b7() -> b1()] = 0
[b7() -> c1()] = 2