(* http://yukicoder.me/problems/19 *)

open System

[<EntryPoint>]
let main argv = 
    let N = Console.ReadLine() |> int
    let W = Console.ReadLine().Split([|' '|]) |> Array.map int
    let total = Array.sum W
    let U = total / 2
    let solve () =
        if U * 2 <> total then false else
        let dp = Array2D.zeroCreate<int> (N+1) (U+1)
        for i = N-1 downto 0 do
            for u = 0 to U do
                if u < W.[i] then
                    dp.[i,u] <- dp.[i+1,u]
                else
                    dp.[i,u] <- max dp.[i+1,u] (dp.[i+1,u-W.[i]] + W.[i])
        dp.[0, U] = U
    if solve () then "possible" else "impossible"
    |> printfn "%s"
    0