n=int(input())
W=list(map(int,input().split()))

half=sum(W)/n
for i in range(2**n):
  total=0
  for j in range(n):
    if i>>j&1:
      total+=W[j]
    if total>half:
      break
  if total==half:
    print('possible')
    exit()
print('impossible')