n=int(input())
w=list(map(int,input().split()))
W=sum(w)
if W%2:
  print("impossible")
  exit()
q=[0]*(W//2+1)
q[0]=1
for v in w:
  for i in reversed(range(W//2)):
    if i+v<=W//2:
      q[i+v]|=q[i]
print(["impossible","possible"][q[W//2]])