title: How to find the first value less than the search key with STL set?
body: <p>For example I have set of values in <code>std::set</code>:</p>
  
  <pre><code>{1, 2, 3, 5, 6}
  </code></pre>
  
  <p>And a search key, let it be 4, I want to find the first val. less than search key, 3 in this case, how to do it?</p>
  
  <p>In Java there're functions <code>greater()</code>, <code>lower()</code> in <code>TreeSet</code></p>