import sys

N = int(input())
W = input().split(' ')
median = 0
list = []
ans = []

for i in range(0,len(W)):
	W[i] = int(W[i])
	median += W[i]
	list.append(0)

if median % 2 == 1:
	print('impossible')
	sys.exit()

median = median // 2

W.sort()

for i in W:

	if i not in ans:
		ans.append(i)

	for j in range(0,len(ans)):
		buf = ans[j] + i

		if buf > median:
			break

		if buf not in ans:
			ans.append(buf)

if median in ans:
	print('possible')
else:
	print('impossible')