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

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

class C:
    def __init__(self, txt: str):
        self.r: F = None
        self.u: B = None
        self.s: B = None
        self.p: B = None
        self.t: E = None
        self.txt = txt

class D:
    def __init__(self, txt: str):
        self.p: C = None
        self.q: B = None
        self.t: B = None
        self.o: B = None
        self.s: E = None
        self.txt = txt

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

class F:
    def __init__(self, txt: str):
        self.z: E = None
        self.x: D = None
        self.y: C = None
        self.txt = txt

c = A("c")
l = B("l")
e = C("e")
k = D("k")
f = E("f")
j = F("j")
m = B("m")
a = D("a")

c.v = f
c.u = f
c.o = f
c.t = e
c.s = j
l.o = c
e.r = j
e.u = m
e.p = m
e.s = l
e.t = f
k.p = e
k.q = m
k.t = m
k.o = m
k.s = f
f.r = a
f.s = c
f.u = c
f.v = e
f.q = m
j.z = f
j.x = a
j.y = e
m.o = c
a.p = e
a.q = l
a.t = l
a.o = m
a.s = f
assert e.r.y.t.txt == "
class A:
    def __init__(self, txt: str):
        self.v: E = None
        self.t: C = None
        self.u: E = None
        self.s: F = None
        self.o: E = None
        self.txt = txt

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

class C:
    def __init__(self, txt: str):
        self.r: F = None
        self.u: B = None
        self.s: B = None
        self.p: B = None
        self.t: E = None
        self.txt = txt

class D:
    def __init__(self, txt: str):
        self.p: C = None
        self.q: B = None
        self.t: B = None
        self.o: B = None
        self.s: E = None
        self.txt = txt

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

class F:
    def __init__(self, txt: str):
        self.z: E = None
        self.x: D = None
        self.y: C = None
        self.txt = txt

c = A("c")
l = B("l")
e = C("e")
k = D("k")
f = E("f")
j = F("j")
m = B("m")
a = D("a")

c.v = f
c.u = f
c.o = f
c.t = e
c.s = j
l.o = c
e.r = j
e.u = m
e.p = m
e.s = l
e.t = f
k.p = e
k.q = m
k.t = m
k.o = m
k.s = f
f.r = a
f.s = c
f.u = c
f.v = e
f.q = m
j.z = f
j.x = a
j.y = e
m.o = c
a.p = e
a.q = l
a.t = l
a.o = m
a.s = f
assert e.r.y.t.txt == "f"