let () =
    let main () =
        let n = int_of_string (read_line ()) in
        let s = read_line () in

        let rec loop_l l acc =
            if l = n then acc else (
                let nn = n - l in
                let a = Array.make nn 0 in
                let rec loop_i i j =
                    if i < nn then (
                        let rec loop_j j =
                            if i + j = nn || s.[j + l] != s.[i + j + l] then j else loop_j (j + 1)
                        in
                        let j = loop_j j in
                        a.(i) <- j;
                        if j = 0 then loop_i (i + 1) j else
                            let rec loop_k k =
                                if i + k = nn || k + a.(k) >= j then k else
                                    let () = a.(i + k) <- a.(k) in
                                    loop_k (k + 1)
                            in
                            let k = loop_k 1 in
                            loop_i (i + k) (j - k)
                    )
                in
                loop_i 1 0;
                let rec loop i acc =
                    if i = nn then acc else loop (i + 1) (max acc (min i a.(i)))
                in
                let acc = loop 1 acc in
                loop_l (l + 1) acc
            )
        in
        let r = loop_l 0 0 in
        Printf.printf "%d\n" r
    in
    main ()