open System
open System.Collections.Generic

[<AutoOpen>]
module Cin =
    let read f = stdin.ReadLine() |> f
    let reada f = stdin.ReadLine().Split() |> Array.map f
    let readChars() = read string |> Seq.toArray
    let readInts() = readChars() |> Array.map (fun x -> Convert.ToInt32(x.ToString()))

[<AutoOpen>]
module Cout =
    let writer = new IO.StreamWriter(new IO.BufferedStream(Console.OpenStandardOutput()))
    let print (s: string) = writer.Write s
    let println (s: string) = writer.WriteLine s
    let inline puts (s: ^a) = string s |> println

// -----------------------------------------------------------------------------------------------------

// -----------------------------------------------------------------------------------------------------

let main() =
    let n = read int
    let ws = reada int |> Array.sort
    let sum = ws |> Array.sum
    let cum = ws |> Array.scan (+) 0
    let mutable ok = false
    for c in cum do
        if c = sum - c then ok <- true

    if ok then "possible" else "impossible"
    |> puts
    ()

// -----------------------------------------------------------------------------------------------------
main()
writer.Dispose()