import math
N = int(raw_input())
W = map(int,raw_input().split())
sumw = sum(W)
if sumw % 2  == 1:
	print 'impossible'
else:
	ans = -1
	W.sort()
	binList = [('{:0'+str(N)+'b}').format(i) for i in range(int(math.pow(2,N)))]
	for b in binList:
		ssum = sum([W[i] for i in range(N) if b[i] == '1'])
		if ssum == sumw / 2:
			ans = 0
			break
	print ('possible' if ans == 0 else 'impossible')