<strong>Input:</strong> words = ["pay","<strong><u>at</u></strong>tention","practice","<u><strong>at</strong></u>tend"], <code>pref </code>= "at"
<strong>Output:</strong> 2
<strong>Explanation:</strong> The 2 strings that contain "at" as a prefix are: "<u><strong>at</strong></u>tention" and "<u><strong>at</strong></u>tend".