old_contents: var express = require('express');
  var app = express();
  
  app.use(express.static(__dirname + '/'));
  
  app.listen(process.env.PORT || 5000);
  
new_contents: var express = require('express');
  var app = express();
  
  app.use(express.static(__dirname + '/public'));
  
  app.listen(process.env.PORT || 5000);
  
subject: change port to env.PORT