Scanf.scanf "%d" (fun n ->
    let s = Array.init n (fun _ -> Scanf.scanf " %s" (fun s -> s)) in
    let t = Array.init n (fun _ -> Scanf.scanf " %s" (fun t -> t)) in
    let rec loop i =
        if s.(i) = t.(i) then loop (i + 1) else i
    in
    let a = loop 0 in
    Printf.printf "%d\n%s\n%s\n" (a + 1) s.(a) t.(a)
)