jasom

(defun process(cells)
  (do ((moves 0 (+ 1 moves))
       (position 0)
       (cell-value (elt cells 0) (ignore-errors (elt cells position))))
      ((null cell-value) (print moves))
    (psetf
     position (+ cell-value position)
     (elt cells position) (1+ cell-value))))

(defun start()