text: function solve() {
      const info = document.querySelector('#info > span');
      const btnDepart = document.querySelector('#depart');
      const btnArrive = document.querySelector('#arrive');
  
      let currentId = 'depot';
      let currentName;
      function depart() {
          fetch(`https://judgetests.firebaseio.com/schedule/${currentId}.json`)
              .then(res => {
                  if(!res.ok){
                      info.textContent = 'Error';
                      throw new Error ('Wrong Id !');
                  }
                  return res.json();
              })
              .then(data => {
                  const { name, next } = data;
                  currentId = next;
                  currentName = name;
                  info.textContent = `Next stop ${currentName}`;
                  btnDepart.disabled = true;
                  btnArrive.disabled = false;
              })
              .catch(console.error);
      }
  
      function arrive() {
          info.textContent = `Arriving at ${currentName}`;
          btnDepart.disabled = false;
          btnArrive.disabled = true;
      }
  
      return {
          depart,
          arrive,
      };
  }
  
  const result = solve();
  