(define n (string->number (read-line)))
(define w (map string->number (string-split (read-line) " ")))
(define dp (make-vector 11000 0))
(define (check n w a)
  (unless (zero? n)
    (letrec*
      ((s (+ a (car w)))
       (check-1 (lambda (i) 
                        (unless (negative? i)
                          (begin 
                            (when (= (vector-ref dp i) 1)
                                  (vector-set! dp (+ i (car w)) 1))
                            (check-1 (- i 1)))))))
      (check-1 10000)
      (check (- n 1) (cdr w) s))))

(let1 sum (fold + 0 w)    
  (print
    (cond ((= (modulo sum 2) 1) "impossible")
          (else
            (vector-set! dp 0 1)
            (check n w 0)
            (if (zero? (vector-ref dp (/ sum 2))) "impossible" "possible")))))