N = int(input())
W = list(map(int, input().split()))
S = sum(W)

dp = [ False ] * (S + 1)
dp[0] = True
for x in W:
	for i in range(S, x - 1, -1):
		if dp[i - x]:
			dp[i] = True

if S % 2 == 1 or not dp[S // 2]:
	print("impossible")
else:
	print("possible")