(defun main (&rest argv)
  (declare (ignorable argv))
  (let* ((n (read))
         (ws (loop repeat n collect (read)))
         (s (reduce #'+ ws)))
    (when (oddp s)
      (format t "impossible~%")
      (return-from main))
    (let* ((s/2 (floor (/ s 2)))
           (dp (make-array (1+ s/2) :initial-element 0)))
      (setf (aref dp 0) 1)
      (loop for w in ws do
        (loop for i downfrom s/2 to 0 do
          (when (<= (+ i w) s/2)
            (setf (aref dp (+ i w)) (logior (aref dp (+ i w)) (aref dp i))))))
      (format t "~a~%" (if (zerop (aref dp s/2))
                           "impossible"
                           "possible")))))

(main)