def rec(i, j):
	#if dp[i][j] != -1:
	#	return dp[i][j]
	if i in dphash and j in dphash[i]:
		return dphash[i][j]
	if i == N:
		if j == 0:
			ret = True
		else:
			ret = False
	else:
		ret = rec(i + 1, j + W[i]) or rec(i + 1, j - W[i])
	if i in dphash:
		dphash[i][j] = ret
	else:
		dphash[i] = {}
		dphash[i][j] = ret
	return ret

N = int(input())
W = list(map(int, input().split()))
#dp = [[-1 for j in range(10001)] for i in range(101)]
dphash = {}
if rec(0, 0):
	print("possible")
else:
	print("impossible")