n=input()
w=sorted(map(int,raw_input().split()))[::-1]
s=sum(w)
if s&1:
	print"impossible"
	exit()
s/=2
def solve(a,b):
	if a>=n:
		return False
	c=b+w[a]
	if c>s:
		return solve(a+1,b)
	if c==s:
		return True
	return solve(a+1,c)
print["im",""][solve(0,0)]+"possible"