import math
N = int(raw_input())
W = map(int,raw_input().split())
sumw = sum(W)
if sumw % 2  == 1:
	print 'impossible'
else:
	queue = [0,0]
	f = False
	while len(queue) > 0:
		ite,now= queue.pop(0),queue.pop(0)
		if ite >= N and now == sumw / 2:
			f = True
			break
		if ite >= N:continue
		if now > sumw / 2:continue
		queue.append(ite + 1)
		queue.append(now + W[ite])
		queue.append(ite + 1)
		queue.append(now)
	if f:
		print 'possible'
	else:
		print 'impossible'