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

class B:
    def __init__(self, txt: str):
        self.v: E = None
        self.x: C = None
        self.t: E = None
        self.z: F = None
        self.u: E = None
        self.y: E = None
        self.txt = txt

class C:
    def __init__(self, txt: str):
        self.y: D = None
        self.u: A = None
        self.v: F = None
        self.z: A = None
        self.q: F = None
        self.o: F = None
        self.txt = txt

class D:
    def __init__(self, txt: str):
        self.s: B = None
        self.r: A = None
        self.t: B = None
        self.txt = txt

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

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

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

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

class B:
    def __init__(self, txt: str):
        self.v: E = None
        self.x: C = None
        self.t: E = None
        self.z: F = None
        self.u: E = None
        self.y: E = None
        self.txt = txt

class C:
    def __init__(self, txt: str):
        self.y: D = None
        self.u: A = None
        self.v: F = None
        self.z: A = None
        self.q: F = None
        self.o: F = None
        self.txt = txt

class D:
    def __init__(self, txt: str):
        self.s: B = None
        self.r: A = None
        self.t: B = None
        self.txt = txt

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

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

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

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