<p>You are given an integer array <code>nums</code> where the largest integer is <strong>unique</strong>.</p>
<p>Determine whether the largest element in the array is <strong>at least twice</strong> as much as every other number in the array. If it is, return <em>the <strong>index</strong> of the largest element, or return </em><code>-1</code><em> otherwise</em>.</p>