N = input()
W = map(int,raw_input().split())
S = sum(W)
if S&1:
	print "impossible"
else:
	S /= 2
	dp = [0]*(S+101)
	dp[0] = 1
	for w in W:
		for i in range(S-1,-1,-1):
			dp[i+w] += dp[i]
	print "possible" if dp[S] else "impossible"