: For alphabet $\backslash$Sigma $=\{$a$,$ b$,$ c$\},$ suppose x in $\backslash$Sigma

$$ and $|$x$|=5.$ Give a

string x

$0$

that is a substring of x and has the following property:

Among all substrings of x$,$ x

$0$

is both a prefix of x and a suffix of x$,$ and is the longest substring

of x$.$