Scanf.scanf "%d %d %d %d %d" (fun a b c d m ->
    let rec loop x y mx =
        if y > d then mx else
        if x > b then loop a (y + 1) mx else
            loop (x + 1) y (max mx ((x + y) mod m))
    in
    loop a b 0 |> Printf.printf "%d\n"
)