title: Openlayer 4 get polygon coordinates after select feature
body: <p>I want get coordinates after select feature using interaction.Select.</p>
  
  <p>Fragment of my code:</p>
  
  <pre><code>  var selectf = new ol.interaction.Select({
      layers: [vectorLayer],
       }); 
     map.addInteraction(selectf); 
  
  
    selectf.on('select', function(evt) {
  
  //here I want read coordinates of selected feature
  }); 
  </code></pre>
  
  <p>How I can do it?</p>