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

class B:
    def __init__(self, txt: str):
        self.y: F = None
        self.s: D = None
        self.txt = txt

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

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

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

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

i = A("i")
b = B("b")
n = C("n")
c = D("c")
l = E("l")
j = F("j")
f = E("f")
g = F("g")
d = E("d")

i.u = f
i.y = c
i.v = c
i.o = n
i.z = d
b.y = j
b.s = c
n.w = f
n.z = f
n.s = l
c.t = j
c.r = i
c.v = f
c.q = f
c.u = b
c.o = n
l.z = b
j.t = b
j.v = i
j.w = i
j.q = g
j.u = n
f.z = b
g.t = b
g.v = i
g.w = i
g.q = j
g.u = n
d.z = b
assert l.z.s.t.v.txt == "
class A:
    def __init__(self, txt: str):
        self.u: E = None
        self.y: D = None
        self.v: D = None
        self.o: C = None
        self.z: E = None
        self.txt = txt

class B:
    def __init__(self, txt: str):
        self.y: F = None
        self.s: D = None
        self.txt = txt

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

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

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

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

i = A("i")
b = B("b")
n = C("n")
c = D("c")
l = E("l")
j = F("j")
f = E("f")
g = F("g")
d = E("d")

i.u = f
i.y = c
i.v = c
i.o = n
i.z = d
b.y = j
b.s = c
n.w = f
n.z = f
n.s = l
c.t = j
c.r = i
c.v = f
c.q = f
c.u = b
c.o = n
l.z = b
j.t = b
j.v = i
j.w = i
j.q = g
j.u = n
f.z = b
g.t = b
g.v = i
g.w = i
g.q = j
g.u = n
d.z = b
assert l.z.s.t.v.txt == "i"