;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Use DP
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

; integer
(defparameter *half* 0)
(defparameter *n* 0)
; list
(defparameter *stack* nil)
(defparameter *ints* nil)
; array
(defparameter *ws* nil)
(defparameter *dp* (make-array (list 101 10001)
			       :initial-element nil))

(defun convert-to-int (c)
  (cond
    ((char= c #\ )
     (push (parse-integer
	     (coerce (reverse *stack*) 'string))
	   *ints*)
     (setf *stack* nil)
     )
    (t (push c *stack*))
    )
  )

(defun set-ws ()
  (setf s (read-line))
  (loop for c across s
	do
	(convert-to-int c)
	finally
	(push (parse-integer
		(coerce (reverse *stack*) 'string))
	      *ints*)
	)
  (setf *ws* (reverse *ints*))
  )

(defun input ()
  (setf *n* (parse-integer (read-line)))
  (set-ws)
  )

(defun initial-setting ()
  (input)
  (loop for w in *ws* summing w into total
	finally (setf *half* (/ total 2))
	)
  (setf (aref *dp* 0 0) t)
  (setf *ws* (make-array (length *ws*)
			 :initial-contents *ws*))
  )

(defun run-dp ()
  (loop for i from 0 to (1- *n*)
	do
	(loop for j from 0 to *half*
	      do
	      (setf (aref *dp* (1+ i) j)
		    (or (aref *dp* (1+ i) j)
			(aref *dp* i j)))
	      (cond ((>= j (aref *ws* i))
		     (setf (aref *dp* (1+ i) j)
			   (or (aref *dp* (1+ i) j)
			       (aref *dp* i (- j (aref *ws* i)))))))
	      )
	)
  (if (aref *dp* *n* *half*)
    (princ "possible")
    (princ "impossible")
    )
  )

(defun n4 ()
  (initial-setting)

  ; A half of total mass must be integer.
  (cond ((null (integerp *half*))
	 (princ "impossible")
	 (return-from n4)))

  (run-dp)

  )

(n4)