title: Using sqrt function in c++
body: <p>So, I am using <code>sqrt</code> function in c++ and the problem I am facing is, when the input to <code>sqrt</code> is <code>40000000001</code>, it returns 200000.</p>
  
  <pre><code>#include &lt;iostream&gt;
  #include &lt;cmath&gt;
  
  using namespace std;
  
  int main (void)
  {
      long long int a;
      cin&gt;&gt;a;
      double b = sqrt(a);
      cout&lt;&lt;b&lt;&lt;"\n";
      return 0;
  }
  </code></pre>
  
  <p>Why is this happening?</p>
  
  <p>It should return 200000.0000025 and I need this exact value. Even getting 200000 produces a Wrong answer. Thanks!</p>