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$f\colon A\to B$, $f\colon x\mapsto x^2$\\
$f\colon A\hookrightarrow B$ \\
$p\Rightarrow q\equiv\neg p\lor q$ \\
$a\equiv 0 \pmod{m} \iff a\bmod m=0$\\
$| \Longleftrightarrow | \iff |$

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