### BUGGY CODE ###

#!/usr/bin/env python3

import sys
# import math
# from string import ascii_lowercase, ascii_upper_case, ascii_letters, digits, hexdigits
# import re                                    # re.compile(pattern) => ptn obj; p.search(s), p.match(s), p.finditer(s) => match obj; p.sub(after, s)
# from operator import itemgetter              # itemgetter(1), itemgetter('key')
# from collections import deque                # deque class. deque(L): dq.append(x), dq.appendleft(x), dq.pop(), dq.popleft(), dq.rotate()
# from collections import defaultdict          # subclass of dict. defaultdict(facroty)
# from collections import Counter              # subclass of dict. Counter(iter): c.elements(), c.most_common(n), c.subtract(iter)
# from heapq import heapify, heappush, heappop # built-in list. heapify(L) changes list in-place to min-heap in O(n), heappush(heapL, x) and heappop(heapL) in O(lgn).
# from heapq import nlargest, nsmallest        # nlargest(n, iter[, key]) returns k-largest-list in O(n+klgn).
# from itertools import count, cycle, repeat   # count(start[,step]), cycle(iter), repeat(elm[,n])
# from itertools import groupby                # [(k, list(g)) for k, g in groupby('000112')] returns [('0',['0','0','0']), ('1',['1','1']), ('2',['2'])]
# from itertools import starmap                # starmap(pow, [[2,5], [3,2]]) returns [32, 9]
# from itertools import product, permutations  # product(iter, repeat=n), permutations(iter[,r])
# from itertools import combinations, combinations_with_replacement
# from itertools import accumulate             # accumulate(iter[, f])
# from functools import reduce                 # reduce(f, iter[, init])
# from functools import lru_cache              # @lrucache ...arguments of functions should be able to be keys of dict (e.g. list is not allowed)
# from bisect import bisect_left, bisect_right # bisect_left(a, x, lo=0, hi=len(a)) returns i such that all(val<x for val in a[lo:i]) and all(val>-=x for val in a[i:hi]).
# from copy import deepcopy                    # to copy multi-dimentional matrix without reference
# from fractions import gcd                    # for Python 3.4 (previous contest @AtCoder)


def main():
    mod = 1000000007                # 10^9+7
    inf = float('inf')              # sys.float_info.max = 1.79...e+308
    inf = 2 ** 64 - 1               # (for fast JIT compile in PyPy) 1.84...e+19
    sys.setrecursionlimit(10**6)    # 1000 -> 1000000
    def input(): return sys.stdin.readline().rstrip()
    def ii():    return int(input())
    def mi():    return map(int, input().split())
    def mi_0():  return map(lambda x: int(x)-1, input().split())
    def lmi():   return list(map(int, input().split()))
    def lmi_0(): return list(map(lambda x: int(x)-1, input().split()))
    def li():    return list(input())
    

    from random import randint
    class RollingHash:
        def __init__(self, s):
            self.s = s    # パターン探索を行われる側の文字列
            self.size = len(s)
            self.hashmod = 2 ** 64 - 1
            self.base = randint(2 ** 10, 2 ** 11)
            self.hash_list = self._make_rolling_hash_list()

        def _make_rolling_hash_list(self):
            hash_list = [0] * (self.size + 1)    # [h(s[0:0]), h(s[0:1]), h(s[0:2]), h(s[0:3]), ..., h(s[0:size])]
            prev = 0
            for i in range(1, self.size + 1):
                hash_num = (prev * self.base + ord(self.s[i-1])) % self.hashmod
                hash_list[i] = hash_num
                prev = hash_num
            return hash_list

        def calc_hash_str(self, pattern):
            """
            pattern のハッシュを計算
            """
            n = len(pattern)
            hash_num = 0
            for i in range(n):
                hash_num = (hash_num + ord(pattern[i]) * pow(self.base, n - 1 - i, self.hashmod)) % self.hashmod
            return hash_num
        
        def calc_interval_hash(self, i, j):
            """
            s[i:j] のハッシュを計算
            """
            return (self.hash_list[j] - self.hash_list[i] * pow(self.base, (j - i), self.hashmod)) % self.hashmod

    
    n = ii()
    s = input()
    if len(list(set(list(s)))) == n:
        print(0)
    else:
        # main
        rolling = RollingHash(s)
        updated = False
        ans = 0
        for span in range((n // 2) + 1, 0, -1):
            d = dict()
            for i in range(n - span + 1):
                j = i + span
                h = rolling.calc_interval_hash(i, j)
                try:
                    right = d[h]
                    if right <= i:
                        ans = span
                        updated = True
                except KeyError:
                    d[h] = j
                if updated:
                    print(ans)
                    exit()


if __name__ == "__main__":
    main()


### FIXED CODE ###

#!/usr/bin/env python3
import sys
from random import randint

def main():
    def input(): return sys.stdin.readline().rstrip()
    def ii():    return int(input())   
    
    class RollingHash:
        def __init__(self, s):
            self.s = s    # パターン探索を行われる側の文字列
            self.size = len(s)
            self.hashmod = 2 ** 64 - 1
            self.base = randint(2 ** 10, 2 ** 11)
            self.hash_list = self._make_rolling_hash_list()

        def _make_rolling_hash_list(self):
            hash_list = [0] * (self.size + 1)    # [h(s[0:0]), h(s[0:1]), h(s[0:2]), h(s[0:3]), ..., h(s[0:size])]
            prev = 0
            for i in range(1, self.size + 1):
                hash_num = (prev * self.base + ord(self.s[i-1])) % self.hashmod
                hash_list[i] = hash_num
                prev = hash_num
            return hash_list
        
        def calc_interval_hash(self, i, j):
            """
            s[i:j] のハッシュを計算
            """
            return (self.hash_list[j] - self.hash_list[i] * pow(self.base, (j - i), self.hashmod)) % self.hashmod

    
    def span_bisect(rolling):
        left = 1    # 絶対に発見成功するとわかっている
        right = (n // 2) + 1    # 絶対に発見失敗するとわかっている
        while right - left > 1:
            d = dict()
            mid_span = left + (right - left) // 2    # 二分探索で今回選ばれた span
            for i in range(n - mid_span + 1):
                j = i + mid_span
                h = rolling.calc_interval_hash(i, j)
                try:
                    first_j = d[h]
                    if first_j <= i:
                        left = mid_span
                        break
                except KeyError:
                    d[h] = j
            else:
                right = mid_span
        return left


    n = ii()
    s = input()
    if len(list(set(list(s)))) == n:
        print(0)
    else:
        # main
        rolling = RollingHash(s)
        print(span_bisect(rolling))


if __name__ == "__main__":
    main()