title: Is there a simple (possibly obfuscated) math expression for the number of days in a given month?
body: <p>For use in cases where a standard library is not available. Assume that the month is given as an unsigned integer.</p>
  <p>I'd be interested in seeing the shortest arithmetic expression that gives the correct answer, allowing or disallowing bitwise operators &amp; masks but not lookup tables. Partial expressions can be saved into a variable for readability to showcase the idea used.</p>