n=input()
w=sorted(map(int,raw_input().split()))[::-1]
s=sum(w)
if s&1:
	print"impossible"
	exit()
s/=2
if s in w:
	print"possible"
	exit()
t=[0]*(s+1)
for i in range(n):
	nt=t[:]
	tw=w[i]
	for j in range(s):
		if j+tw<=s and t[j]+tw<=s:
			nt[j+tw]=max(t[j+tw],t[j]+tw)
	t=nt
#print t
#print s
print["im",""][s==t[-1]]+"possible"