n = int(input())
w = list(map(int,input().split()))
if sum(w) % 2 == 1:
	print("impossible")
	exit()

W = sum(w) // 2

dp = [0] * (W+1)
dp[0] = 1
for i in w:
	for j in range(W,-1,-1):
		if j + i <= W:
			dp[j+i] |= dp[j]

if dp[W]:
	print("possible")
else:
	print("impossible")