class A:
    def __init__(self, txt: str):
        self.t: B = None
        self.q: C = None
        self.txt = txt

class B:
    def __init__(self, txt: str):
        self.o: C = None
        self.u: A = None
        self.txt = txt

class C:
    def __init__(self, txt: str):
        self.t: B = None
        self.txt = txt

i = A("i")
b = B("b")
l = C("l")
k = A("k")
e = B("e")
n = A("n")

i.t = e
i.q = l
b.o = l
b.u = i
l.t = b
k.t = b
k.q = l
e.o = l
e.u = n
n.t = b
n.q = l
assert l.t.u.q.t.o.t.txt == "
class A:
    def __init__(self, txt: str):
        self.t: B = None
        self.q: C = None
        self.txt = txt

class B:
    def __init__(self, txt: str):
        self.o: C = None
        self.u: A = None
        self.txt = txt

class C:
    def __init__(self, txt: str):
        self.t: B = None
        self.txt = txt

i = A("i")
b = B("b")
l = C("l")
k = A("k")
e = B("e")
n = A("n")

i.t = e
i.q = l
b.o = l
b.u = i
l.t = b
k.t = b
k.q = l
e.o = l
e.u = n
n.t = b
n.q = l
assert l.t.u.q.t.o.t.txt == "b"