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