N=int(input())
A=list(map(int,input().split()))
def chk(li):
  s=sum(li)
  if s%2==1: return "impossible"
  li.sort()
  c=0
  for v in li:
    c+=v
    if c==s//2: return "possible"
    if c>s//2: return "impossible"
  return "impossible"
print(chk(A))