let [| n; s; t; k |] =
    stdin.ReadLine().Split()
    |> Array.map int

let xs =
    stdin.ReadLine().Split()
    |> Array.map int

if xs.[s - 1] + xs.[t - 1] <= k then
    1
else
    let min =
        xs
        |> Array.min

    if min + xs.[t - 1] <= k then
        2
    else
        -1
|> printfn "%d"