Solution
= Solution
<Fermat's little theorem> says that for a <prime number> $p$ and any <integer> $a$,
$$
\boxed{a^p\equiv a\pmod p}.
$$
If $p\nmid a$, cancellation gives the equivalent statement $a^{p-1}\equiv1\pmod p$.
= Solution
<Fermat's little theorem> says that for a <prime number> $p$ and any <integer> $a$,
$$
\boxed{a^p\equiv a\pmod p}.
$$
If $p\nmid a$, cancellation gives the equivalent statement $a^{p-1}\equiv1\pmod p$.