class A:
    def __init__(self, txt: str):
        self.o: B = None
        self.p: D = None
        self.z: F = None
        self.x: F = None
        self.t: C = None
        self.txt = txt

class B:
    def __init__(self, txt: str):
        self.p: A = None
        self.t: D = None
        self.y: E = None
        self.u: E = None
        self.txt = txt

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

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

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

class F:
    def __init__(self, txt: str):
        self.s: D = None
        self.o: D = None
        self.w: C = None
        self.z: D = None
        self.r: C = None
        self.txt = txt

i = A("i")
a = B("a")
m = C("m")
n = D("n")
f = E("f")
c = F("c")
d = D("d")
k = B("k")

i.o = a
i.p = d
i.z = c
i.x = c
i.t = m
a.p = i
a.t = d
a.y = f
a.u = f
m.w = i
m.s = d
m.z = f
m.t = f
m.v = n
n.u = k
n.o = m
n.z = m
n.s = a
n.p = i
f.r = c
f.s = c
f.p = m
c.s = n
c.o = n
c.w = m
c.r = m
c.z = d
d.u = k
d.o = m
d.z = m
d.s = a
d.p = i
k.p = i
k.t = n
k.y = f
k.u = f
assert n.o.t.p.v.txt == "
class A:
    def __init__(self, txt: str):
        self.o: B = None
        self.p: D = None
        self.z: F = None
        self.x: F = None
        self.t: C = None
        self.txt = txt

class B:
    def __init__(self, txt: str):
        self.p: A = None
        self.t: D = None
        self.y: E = None
        self.u: E = None
        self.txt = txt

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

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

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

class F:
    def __init__(self, txt: str):
        self.s: D = None
        self.o: D = None
        self.w: C = None
        self.z: D = None
        self.r: C = None
        self.txt = txt

i = A("i")
a = B("a")
m = C("m")
n = D("n")
f = E("f")
c = F("c")
d = D("d")
k = B("k")

i.o = a
i.p = d
i.z = c
i.x = c
i.t = m
a.p = i
a.t = d
a.y = f
a.u = f
m.w = i
m.s = d
m.z = f
m.t = f
m.v = n
n.u = k
n.o = m
n.z = m
n.s = a
n.p = i
f.r = c
f.s = c
f.p = m
c.s = n
c.o = n
c.w = m
c.r = m
c.z = d
d.u = k
d.o = m
d.z = m
d.s = a
d.p = i
k.p = i
k.t = n
k.y = f
k.u = f
assert n.o.t.p.v.txt == "n"