N = int(raw_input())
W = map(int,raw_input().split())
sumW = sum(W)
W.sort()
if sumW % 2 == 1:
	print 'impossible'
else:
	s = 0
	i = 0
	while s < sumW /2:
		s += W[i]
		i += 1
	if s == sumW / 2:
		print 'possible'
	else:
		print 'impossible'