title: How to insert value in map?
body: <p>I am having an issue with map. </p>
  
  <pre><code>map&lt;int, map&lt;int , int&gt;&gt; my_map;
  </code></pre>
  
  <p>I am using <code>insert()</code> like:</p>
  
  <pre><code>my_map.insert(10, my_map.second.insert(20, 30));
  </code></pre>
  
  <p>but it's not working.</p>