def rec(i, j):
	if i == N:
		if j == 0:
			return True
		else:
			return False
	return rec(i + 1, j + W[i]) or rec(i + 1, j - W[i])

N = int(input())
W = list(map(int, input().split()))
if rec(0, 0):
	print("possible")
else:
	print("impossible")