deletions | additions       diff --git a/4b3.tex b/4b3.tex  index 2d5ca48..c95bb93 100644  --- a/4b3.tex  +++ b/4b3.tex 
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\begin{equation}  \begin{split}  & I \a \neg B \to R\\  \iff & (i \leq n + 1) \a (res = (i - 1)!) \a (i > n) \to res = n!\\  \iff & (i = n + 1) \a (res = (i - 1)!) \to res = n!\\  \iff & res = n! \to res = n!\\  \end{split}  \end{equation}