let size = 100*100+5
let N    = stdin.ReadLine() |> int
let W    = stdin.ReadLine().Split() |> Array.map(int)
let sum  = W |> Array.sum
if sum%2 = 0 then 
    let dp = Array.zeroCreate size
    dp.[0] <- true    
    W
    |> Array.iter (fun x ->
        for i in size-1 .. (-1) .. 0 do
            if dp.[i] then
                dp.[i+x] <- true)                            
    if dp.[sum/2] then "possible"
    else               "impossible"
else 
    "impossible"
|> printfn "%s"