Is this word Lexically Ordered? Given an input string S, return truthy if all the letters in S are Lexically Ordered: their ASCII values need to be in either ascending or descending order. Return falsy in other cases.
Input

Input will be in the same case (all upper- or all lowercase). Your submission should be able to handle both.
Input will consist of ASCII in the range [A-Za-z] only
Input length will be at least 1, up to whatever maximum your language supports.
Input is a string - not a list of characters, not an array of ASCII-codepoints.

Output

Output should be true or false, or 0/1, or any other distinct true / false style output your language can provide.
All true cases need to have the same output, as well as all the false cases. No &quot;False is 0, true is 1, 2, or 3&quot;.

Additional rules

Standard loopholes are forbidden
Answer must be a full program or a function, not a snippet or a REPL-entry.
code-golf, shortest answer in bytes wins.

Test cases
Truthy
&quot;ABCDEF&quot;
&quot;ZYX&quot;
&quot;no&quot;
&quot;tree&quot;   --&gt; the multiple 'e's don't break the order
&quot;q&quot;

Falsy
&quot;ABCDC&quot;
&quot;yes&quot;
&quot;deed&quot;

Invalid
&quot;Hello&quot; --&gt; invalid input - mixed case-, does not have to be handled
&quot;&quot;      --&gt; invalid input - length 0-, does not have to be handled
&quot;\n
  &quot;     --&gt; invalid input - newline is not in range [A-Za-z]-, does not have to be handled
Python 2, 53 44 40 39 bytes



lambda a:`sorted(a)`[2::5]in(a,a[::-1])


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