[ruslan_mart]

window.addEventListener('DOMContentLoaded', function() {

   function taskai(){
      var a = +prompt("iveskite skaiciu");
      var b = +elem.innerHTML + +a;
      localStorage.setItem('taskai', b);
      elem.innerHTML = b;
   }

   var elem = document.getElementById("taskas");
   elem.innerHTML = localStorage.getItem('taskai') || '';

});