n = int(raw_input())
W = map(int, raw_input().split())

a = [0 for _ in range(sum(W)+1)]
a[0] = 1
for i in W:
	for j in range(sum(W))[::-1]:
		if a[j]:
			a[i+j] = 1
print "possible" if sum(W)%2==0 and a[sum(W)/2] else "impossible"