N, W = int(raw_input()), map(int, raw_input().split())
total = sum(W)

if total % 2 == 1:
	print 'impossible'
	exit()

half = total / 2
dp = [False] * (half + 1)
dp[0] = True

for i in xrange(N):
	for j in xrange(half, -1, -1):
		if j - W[i] >= 0:
			dp[j] |= dp[j - W[i]]

if dp[half]:
	print 'possible'
else:
	print 'impossible'