<p>Given an integer array <code>nums</code>, return <em>the number of elements that have <strong>both</strong> a strictly smaller and a strictly greater element appear in </em><code>nums</code>.</p>
<strong>Explanation:</strong> The element 3 has the element -3 strictly smaller than it and the element 90 strictly greater than it.
Since there are two elements with the value 3, in total there are 2 elements having both a strictly smaller and a strictly greater element appear in <code>nums</code>.