text: const express = require('express')
  const app = express()
  const port = 3001
  
  let counter = -1;
  
  app.get('/', (req, res) => {
    counter++;
    res.send(`pong ${counter}`);
  })
  
  app.listen(port, () => {
    console.log(`Ping pong app listening at http://localhost:${port}`)
  })