n = int(input())

arr = map(int,raw_input().split())

accumlate = sum(arr)
if accumlate %2 == 1:
	print 'impossible'
	quit()

dp = [0 for i in range(accumlate/2 + 1)]
dp[0] = 1

for i in arr:
	tmp = dp[::1]
	for j in range(accumlate/2+1):
		if j - i > -1 and dp[j-i] == 1:
			tmp[j] = 1

	dp = tmp[::1]

print 'possible' if dp[accumlate/2] else 'impossible'