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

for i in W:
	for j in range(0,len(list)):
		buf = list[j] + i
		if buf not in ans:
			ans.append(buf)

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

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