Scanf.scanf "%d %d %d" (fun n m x ->
    let nei = Array.make n [] in
    for i = 1 to m do
        Scanf.scanf " %d %d %d %d" (fun u v c t ->
            let u = u - 1 in
            let v = v - 1 in
            nei.(u) <- (v, c + t * x) :: nei.(u);
            nei.(v) <- (u, c + t * x) :: nei.(v);
        )
    done;
    let sentinel = max_int / 10 in
    let dist = Array.make n sentinel in
    dist.(0) <- 0;
    let module S = Set.Make (struct type t = int * int let compare = compare end) in

    let rec loop set =
        if S.is_empty set then dist.(n - 1) else
            let ((cost, pos) as mi) = S.min_elt set in
            let set = S.remove mi set in
            if dist.(pos) <> cost then loop set else
                let set =
                    List.fold_left (fun set (next, c0) ->
                        if dist.(next) > c0 + cost then (dist.(next) <- c0 + cost; S.add (c0 + cost, next) set)
                        else set) set nei.(pos)
                in
                loop set
    in
    let v = loop (S.singleton (0, 0)) in
    Printf.printf "%d\n" @@ if v = sentinel then (-1) else (v + x - 1) / x
)