02. Fibonacci

function getFibonator() {
  let f0 = 0;
  let f1 = 1;

  function fibunachi() {
    const oldf0 = f0;
    const oldf1 = f1;

    f0 = oldf1;
    f1 = oldf0 + oldf1;

    return f0;
  }


  return fibunachi;
}