N = int(raw_input())
W = map(int, raw_input().split())
sum = 0
for i in range(0, N):
	sum += W[i]
if sum % 2 == 1: print 'impossible'
else:
	dp = []
	for i in range(0, N+1):
		lst = []
		for j in range(0, sum+1):
			lst.append(False)
		dp.append(lst)
	dp[0][0] = True
	for i in range(0, N):
		for j in range(0, sum+1):
			if dp[i][j]:
				dp[i+1][j] = True
				dp[i+1][j+W[i]] = True
	if dp[N][sum/2]: print 'possible'
	else: print 'impossible'