-- yukicoder My Practice
-- author: Leonardone @ NEETSDKASU
-- http://yukicoder.me/problems/19

import Data.List
import qualified Data.Set as Set

main = do
    n <- getLine
    w <- getLine
    putStrLn $ main' n w

main' n ws =
    let
        w = map read $ words ws
        s = sum w
        h = s `div` 2
    in
        if h * 2 == s && solve h [0] w Set.empty then "possible" else "impossible"

solve _ _ [] _ = False
solve s [] (x:xs) ls = 
    let lls = Set.insert x ls
    in solve s (Set.toList lls) xs Set.empty
solve s (t:ts) (x:xs) ls
    | y == s = True
    | y > s = slv lls
    | y < s = slv (Set.insert y lls)
    where
        y = t + x
        lls = Set.insert t ls
        slv = solve s ts (x:xs)