title: Search in std::map for key that bounds the search value
body: <p>Suppose if I have <code>std::map&lt;std::pair&lt;int, int&gt;, int&gt;</code> with key in map as a pair of two integer values.</p>
  
  <p>Is it possible to find a key that bounds the value I am looking for?</p>
  
  <p>For example: if map contains:</p>
  
  <pre><code>key = {4, 9}
  </code></pre>
  
  <p>Can I find this key based on that <code>x</code> is greater than 4 and <code>x</code> is smaller than 9? Where <code>x</code> is some integer value.</p>
  
  <p>I hope it makes sense.</p>