Scanf.scanf "%d" (fun n ->
    let a = Array.init (n + 1) (fun _ -> Scanf.scanf " %d" (fun a -> a)) in
    let b = Array.init (n + 1) (fun _ -> Scanf.scanf " %d" (fun b -> b)) in

    let z = 1_000_000_007 in
    let ( +@) a b = (a + b) mod z in
    let ( *@) a b = (a * b) mod z in

    let rec loop i bsum acc =
        if i < 0 then acc else
            let bsum = bsum +@ b.(n - i) in
            let acc = acc +@ a.(i) *@ bsum in
            loop (i - 1) bsum acc
    in
    loop n 0 0 |> Printf.printf "%d\n"
)