title: what library to use for stoi keyword in c++
body: <p>my question is pretty simple but I can't seem to find it out.
  I want to know what libary to include when using <code>stoi</code>. I was using <code>atoi</code> and it works fine with </p>
  
  <pre><code>#include &lt;iostream&gt;
  #include &lt;string&gt;
  #include &lt;stdlib.h&gt;
  using namespace std;
  </code></pre>
  
  <p>but I get "stoi not declared" when I run with <code>stoi</code>. Thanks</p>