title: Sum Integers written into a String
body: <p>I used </p>
  
  <pre><code>int num = Integer.parseInt(str)
  </code></pre>
  
  <p>to written integer values into a string.I need a function that reads these values
  from given string and calculates their sum.</p>
  
  <p>Example: input - "43 68 9 23 318" 
  output - 461 </p>