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


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

main' n ws =
    let
        w = map read $ words ws
        s = foldl1 (+) w `div` 2
    in
        if solve s 0 w then "possible" else "impossible"

solve s p [] = s == p
solve s p (x:xs) = solve s (p + x) xs || solve s p xs