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

class B:
    def __init__(self, txt: str):
        self.x: E = None
        self.r: C = None
        self.txt = txt

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

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

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

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

j = A("j")
g = B("g")
m = C("m")
b = D("b")
a = E("a")
d = F("d")
i = F("i")
l = A("l")
k = E("k")
c = D("c")

j.v = i
j.x = i
j.u = i
j.q = m
j.z = m
j.o = d
g.x = a
g.r = m
m.t = i
b.y = i
b.t = i
b.x = m
a.u = k
d.z = c
d.x = a
i.z = b
i.x = a
l.v = i
l.x = i
l.u = i
l.q = m
l.z = m
l.o = d
k.u = a
c.y = d
c.t = d
c.x = m
assert m.t.x.u.txt == "
class A:
    def __init__(self, txt: str):
        self.v: F = None
        self.q: C = None
        self.x: F = None
        self.o: F = None
        self.z: C = None
        self.u: F = None
        self.txt = txt

class B:
    def __init__(self, txt: str):
        self.x: E = None
        self.r: C = None
        self.txt = txt

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

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

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

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

j = A("j")
g = B("g")
m = C("m")
b = D("b")
a = E("a")
d = F("d")
i = F("i")
l = A("l")
k = E("k")
c = D("c")

j.v = i
j.x = i
j.u = i
j.q = m
j.z = m
j.o = d
g.x = a
g.r = m
m.t = i
b.y = i
b.t = i
b.x = m
a.u = k
d.z = c
d.x = a
i.z = b
i.x = a
l.v = i
l.x = i
l.u = i
l.q = m
l.z = m
l.o = d
k.u = a
c.y = d
c.t = d
c.x = m
assert m.t.x.u.txt == "k"