(let* ((n (string->number (read-line)))
       (arr (map string->number (string-split (read-line) #\space))))
  (define vec (make-vector (* 100 n) #f))
  (define total (fold + 0 arr))

  (vector-set! vec 0 #t)

  (let loop ((weights arr))
    (cond ((null? weights)
	   (if (or (= (mod total 2) 1) (eqv? (vector-ref vec (div total 2)) #f))
	       (print "impossible")
	       (print "possible")))
	  (else
	   (for-each
	    (lambda (j)
	      (let1 pred (- j (car weights))
		    (if (and (>= pred 0) (vector-ref vec pred))
			(vector-set! vec j #t))))
	    (iota (* 100 n)))
	   (loop (cdr weights))))))