### BUGGY CODE ###

mod = 10 ** 9 + 7
mod2 = 2**61+1
from collections import deque
import heapq


def iip(listed):
    ret = [int(i) for i in input().split()]
    if len(ret) == 1 and not listed:
        return ret[0]
    return ret


def main():
    r = solve()
    print(r)

def solve():
    N = iip(False)
    S = input()
    S = [ord(i) for i in S]

    ln = len(S)

    def same(l):
        for l1 in range(0, ln-l):
            h1t = 0
            h2t = 0
            b1 = 26
            b2 = 27
            k1 = 1
            k2 = 1
            for i in range(l): # 検索対象のhashを作る
                ht = S[l1 + l - 1 - i]
                h1t += ht * k1
                h2t += ht * k2
                k1 *= b1
                k2 *= b2

                h1t %= mod2
                h2t %= mod2
                k1 %= mod2
                k2 %= mod2

            h1s = 0
            h2s = 0
            k1 = 1
            k2 = 1
            for i in range(l): #最初の比較対象hashを作る
                if l1 + l + l - 1 >= ln:
                    return False
                ht = S[l1 + l + l - 1 - i]
                h1s += ht*k1
                h2s += ht*k2

                k1 *= b1
                k2 *= b2

                h1s %= mod2
                h2s %= mod2
                k1 %= mod2
                k2 %= mod2
                if h1t == h1s and h2t == h2s:
                    return True

            for i in range(l1+l+l, ln):
                h1s = h1s * b1 + S[i] - S[i-l]* power(b1, l, mod2)
                h2s = h2s * b2 + S[i] - S[i-l]* power(b2, l, mod2)
                if h1t == h1s and h2t == h2s:
                    return True

        return False


    mn = 0
    mx = ln // 2+1
    while mx - mn > 1:
        l = (mx+mn) // 2

        is_same = same(l)

        if is_same:
            mn = l
        else:
            mx = l

    #print(mn, mx)
    return mn


#####################################################ライブラリ集ここから

def split_print_space(s):
    print(" ".join([str(i) for i in s]))


def split_print_enter(s):
    print("\n".join([str(i) for i in s]))


def koenai_saidai_x_index(sorted_list, n):
    l = 0
    r = len(sorted_list)
    if len(sorted_list) == 0:
        return False
    if sorted_list[0] > n:
        return False

    while r - l > 1:
        x = (l + r) // 2
        if sorted_list[x] == n:
            return x
        elif sorted_list[x] > n:
            r = x
        else:
            l = x
    return l


def searchsorted(sorted_list, n, side):
    if side not in ["right", "left"]:
        raise Exception("sideはrightかleftで指定してください")

    l = 0
    r = len(sorted_list)

    if n > sorted_list[-1]:
        # print(sorted_list)
        return len(sorted_list)
    if n < sorted_list[0]:
        return 0

    while r - l > 1:
        x = (l + r) // 2
        if sorted_list[x] > n:
            r = x
        elif sorted_list[x] < n:
            l = x
        else:
            if side == "left":
                r = x
            elif side == "right":
                l = x

    if side == "left":
        if sorted_list[l] == n:
            return r - 1
        else:
            return r

    if side == "right":
        if sorted_list[l] == n:
            return l + 1
        else:
            return l


def soinsuu_bunkai(n):
    ret = []
    for i in range(2, int(n ** 0.5) + 1):
        while n % i == 0:
            n //= i
            ret.append(i)
        if i > n:
            break
    if n != 1:
        ret.append(n)
    return ret


def conbination(n, r, mod, test=False):
    if n <= 0:
        return 0
    if r == 0:
        return 1
    if r < 0:
        return 0
    if r == 1:
        return n
    ret = 1
    for i in range(n - r + 1, n + 1):
        ret *= i
        ret = ret % mod

    bunbo = 1
    for i in range(1, r + 1):
        bunbo *= i
        bunbo = bunbo % mod

    ret = (ret * inv(bunbo, mod)) % mod
    if test:
        # print(f"{n}C{r} = {ret}")
        pass
    return ret


def inv(n, mod):
    return power(n, mod - 2)


def power(n, p, mod_= mod):
    if p == 0:
        return 1
    if p % 2 == 0:
        return (power(n, p // 2) ** 2) % mod_
    if p % 2 == 1:
        return (n * power(n, p - 1)) % mod_


if __name__ == "__main__":
    main()

### FIXED CODE ###

mod = 10 ** 9 + 7
mod2 = 2**61+1
from collections import deque
import heapq


def iip(listed):
    ret = [int(i) for i in input().split()]
    if len(ret) == 1 and not listed:
        return ret[0]
    return ret


def main():
    r = solve()
    print(r)

def solve():
    N = iip(False)
    S = input()
    S = [ord(i) for i in S]

    ln = len(S)

    def same(l):
        h1 = 0
        h2 = 0
        b1 = 26
        b2 = 27
        k1 = 1
        k2 = 1
        bl1 = power(b1, l, mod2)
        bl2 = power(b2, l, mod2)
        for i in range(l):  # 最初の検索対象のhashを作る
            ht = S[l - 1 - i]
            h1 += ht * k1
            h2 += ht * k2
            k1 *= b1
            k2 *= b2

            h1 %= mod2
            h2 %= mod2
            k1 %= mod2
            k2 %= mod2

        hl1 = [h1]
        hl2 = [h2]
        for i in range(l, ln):
            h1 = h1 * b1 + S[i] - S[i-l]* bl1
            h2 = h2 * b2 + S[i] - S[i-l]* bl2
            h1 %= mod2
            h2 %= mod2
            hl1.append(h1)
            hl2.append(h2)

        #print(hl1)
        lnh = len(hl1)
        for i in range(lnh):
            for j in range(lnh):
                if i-j < l:
                    continue
                if hl1[i] == hl1[j] and hl2[i] == hl2[j]:
                    return True


        return False


    mn = 0
    mx = ln // 2+1
    while mx - mn > 1:
        l = (mx+mn) // 2

        is_same = same(l)

        if is_same:
            mn = l
        else:
            mx = l

    #print(mn, mx)
    return mn


#####################################################ライブラリ集ここから

def split_print_space(s):
    print(" ".join([str(i) for i in s]))


def split_print_enter(s):
    print("\n".join([str(i) for i in s]))


def koenai_saidai_x_index(sorted_list, n):
    l = 0
    r = len(sorted_list)
    if len(sorted_list) == 0:
        return False
    if sorted_list[0] > n:
        return False

    while r - l > 1:
        x = (l + r) // 2
        if sorted_list[x] == n:
            return x
        elif sorted_list[x] > n:
            r = x
        else:
            l = x
    return l


def searchsorted(sorted_list, n, side):
    if side not in ["right", "left"]:
        raise Exception("sideはrightかleftで指定してください")

    l = 0
    r = len(sorted_list)

    if n > sorted_list[-1]:
        # print(sorted_list)
        return len(sorted_list)
    if n < sorted_list[0]:
        return 0

    while r - l > 1:
        x = (l + r) // 2
        if sorted_list[x] > n:
            r = x
        elif sorted_list[x] < n:
            l = x
        else:
            if side == "left":
                r = x
            elif side == "right":
                l = x

    if side == "left":
        if sorted_list[l] == n:
            return r - 1
        else:
            return r

    if side == "right":
        if sorted_list[l] == n:
            return l + 1
        else:
            return l


def soinsuu_bunkai(n):
    ret = []
    for i in range(2, int(n ** 0.5) + 1):
        while n % i == 0:
            n //= i
            ret.append(i)
        if i > n:
            break
    if n != 1:
        ret.append(n)
    return ret


def conbination(n, r, mod, test=False):
    if n <= 0:
        return 0
    if r == 0:
        return 1
    if r < 0:
        return 0
    if r == 1:
        return n
    ret = 1
    for i in range(n - r + 1, n + 1):
        ret *= i
        ret = ret % mod

    bunbo = 1
    for i in range(1, r + 1):
        bunbo *= i
        bunbo = bunbo % mod

    ret = (ret * inv(bunbo, mod)) % mod
    if test:
        # print(f"{n}C{r} = {ret}")
        pass
    return ret


def inv(n, mod):
    return power(n, mod - 2)


def power(n, p, mod_= mod):
    if p == 0:
        return 1
    if p % 2 == 0:
        return (power(n, p // 2, mod_) ** 2) % mod_
    if p % 2 == 1:
        return (n * power(n, p - 1, mod_)) % mod_


if __name__ == "__main__":
    main()