class A:
    def __init__(self, txt: str):
        self.y: E = None
        self.s: E = None
        self.txt = txt

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

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

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

class E:
    def __init__(self, txt: str):
        self.q: F = None
        self.v: A = None
        self.u: B = None
        self.s: C = None
        self.txt = txt

class F:
    def __init__(self, txt: str):
        self.v: A = None
        self.o: A = None
        self.s: A = None
        self.z: E = None
        self.x: B = None
        self.txt = txt

e = A("e")
m = B("m")
i = C("i")
l = D("l")
n = E("n")
f = F("f")
c = C("c")

e.y = n
e.s = n
m.u = l
m.t = i
i.o = l
i.u = c
i.v = c
i.q = n
i.s = n
l.v = i
l.x = e
n.q = f
n.v = e
n.u = m
n.s = i
f.v = e
f.o = e
f.s = e
f.z = n
f.x = m
c.o = l
c.u = i
c.v = i
c.q = n
c.s = n
assert m.u.x.s.txt == "
class A:
    def __init__(self, txt: str):
        self.y: E = None
        self.s: E = None
        self.txt = txt

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

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

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

class E:
    def __init__(self, txt: str):
        self.q: F = None
        self.v: A = None
        self.u: B = None
        self.s: C = None
        self.txt = txt

class F:
    def __init__(self, txt: str):
        self.v: A = None
        self.o: A = None
        self.s: A = None
        self.z: E = None
        self.x: B = None
        self.txt = txt

e = A("e")
m = B("m")
i = C("i")
l = D("l")
n = E("n")
f = F("f")
c = C("c")

e.y = n
e.s = n
m.u = l
m.t = i
i.o = l
i.u = c
i.v = c
i.q = n
i.s = n
l.v = i
l.x = e
n.q = f
n.v = e
n.u = m
n.s = i
f.v = e
f.o = e
f.s = e
f.z = n
f.x = m
c.o = l
c.u = i
c.v = i
c.q = n
c.s = n
assert m.u.x.s.txt == "n"