title: Summing values of a column using awk command
body: <p>I want to sum the values of all rows in the column 3. How can I do this?</p>
  
  <p>Input:</p>
  
  <pre><code>chr19   10 11
  chr19   12 15
  chr19   11 29
  chr19   a0 20
  </code></pre>
  
  <p>Expected output:</p>
  
  <p><code>75</code></p>