import Data.Array
import Data.Maybe (fromJust)
main = do
  n <- read <$> getLine
  ws <- map read . words <$> getLine
  let
    sumOfWs = sum ws
    table = listArray ((1,1),(n,div sumOfWs 2)) $ repeat Nothing
  putStrLn $ if even sumOfWs && snd (partition table n (div sumOfWs 2) ws) then "possible" else "impossible"

partition table n m []
  | m == 0 = (table,True)
  | otherwise = (table,False)
partition table n m (w:ws)
  | m < 0 = (table,False)
  | m == 0 = (table,True)
  | otherwise = case table!(n,m) of
      Just b -> (table,b)
      Nothing -> (table2//[((n,m),Just result)],result)
      where
        (table1,r1) = partition table (n-1) m ws
        (table2,r2) = partition table1 (n-1) (m-w) ws
        result = r1 || r2