How to find a missing file from a directory
<p>I have a directory in which 'wav' files are stored. These files's names are sequential in order ie 1.wav, 2.wav, 3.wav.... etc.</p>

<p>I have to find out the missing wav file, like if 3.wav is missing then I have to find out that and the name '3' should given to a variable.</p>

<p>How can I do this?</p>
