y \overset{A}{\underset{B}{\Downarrow}}) \underset{B}{\Downarrow} ~
+
y \overset{A}{\underset{B}{\Downarrow}}
−
z \overset{B}{\underset{C}{\Downarrow}}) \underset{C}{\Downarrow}
+
) \overset{ }{\underset{B}{\Downarrow}} ~
+
z \overset{B}{\underset{C}{\Downarrow}}
+
) \overset{ }{\underset{C}{\Downarrow}}
\\ \\
\\ \\
=
=
\\ \\
\\ \\
−
(x \underset{A}{\Downarrow} ~
+
(x \overset{ }{\underset{A}{\Downarrow}} ~
(y \overset{A}{\underset{B}{\Downarrow}} ~
(y \overset{A}{\underset{B}{\Downarrow}} ~
(z \overset{B}{\underset{C}{\Downarrow}} ~
(z \overset{B}{\underset{C}{\Downarrow}} ~
−
P \overset{B \Rightarrow C}{\underset{(A \Rightarrow B) \Rightarrow (A \Rightarrow C)}{\Downarrow}})\overset{A \Rightarrow B}{\underset{B \Rightarrow C}{\Downarrow}} )\overset{A}{\underset{C}{\Downarrow}})\underset{C}{\Downarrow}
+
P \overset{B \Rightarrow C}{\underset{(A \Rightarrow B) \Rightarrow (A \Rightarrow C)}{\Downarrow}}