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

class B:
    def __init__(self, txt: str):
        self.u: D = None
        self.z: B = None
        self.txt = txt

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

class D:
    def __init__(self, txt: str):
        self.v: D = None
        self.u: C = None
        self.txt = txt

e = A("e")
l = B("l")
i = C("i")
h = D("h")
b = D("b")
n = A("n")
k = C("k")
f = C("f")
m = B("m")
c = D("c")

e.o = k
e.v = c
e.t = m
l.u = c
l.z = m
i.x = k
i.u = e
i.o = h
i.s = l
h.v = b
h.u = i
b.v = c
b.u = i
n.o = i
n.v = b
n.t = m
k.x = f
k.u = e
k.o = h
k.s = m
f.x = i
f.u = e
f.o = b
f.s = l
m.u = h
m.z = l
c.v = h
c.u = k
assert n.o.o.u.x.s.txt == "
class A:
    def __init__(self, txt: str):
        self.o: C = None
        self.v: D = None
        self.t: B = None
        self.txt = txt

class B:
    def __init__(self, txt: str):
        self.u: D = None
        self.z: B = None
        self.txt = txt

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

class D:
    def __init__(self, txt: str):
        self.v: D = None
        self.u: C = None
        self.txt = txt

e = A("e")
l = B("l")
i = C("i")
h = D("h")
b = D("b")
n = A("n")
k = C("k")
f = C("f")
m = B("m")
c = D("c")

e.o = k
e.v = c
e.t = m
l.u = c
l.z = m
i.x = k
i.u = e
i.o = h
i.s = l
h.v = b
h.u = i
b.v = c
b.u = i
n.o = i
n.v = b
n.t = m
k.x = f
k.u = e
k.o = h
k.s = m
f.x = i
f.u = e
f.o = b
f.s = l
m.u = h
m.z = l
c.v = h
c.u = k
assert n.o.o.u.x.s.txt == "m"