<p>Given a string <code>s</code> which consists of lowercase or uppercase letters, return <em>the length of the <strong>longest palindrome</strong></em>&nbsp;that can be built with those letters.</p>

<p>Letters are <strong>case sensitive</strong>, for example,&nbsp;<code>&quot;Aa&quot;</code> is not considered a palindrome here.</p>

<p>&nbsp;</p>
<p><strong>Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;abccccdd&quot;
<strong>Output:</strong> 7
<strong>Explanation:</strong>
One longest palindrome that can be built is &quot;dccaccd&quot;, whose length is 7.
</pre>

<p><strong>Example 2:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;a&quot;
<strong>Output:</strong> 1
</pre>

<p><strong>Example 3:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;bb&quot;
<strong>Output:</strong> 2
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 2000</code></li>
	<li><code>s</code> consists of lowercase <strong>and/or</strong> uppercase English&nbsp;letters only.</li>
</ul>