# Original solution
# -*- coding: utf-8 -*-
import bisect
import heapq
import math
import random
import sys
from collections import Counter, defaultdict, deque
from decimal import ROUND_CEILING, ROUND_HALF_UP, Decimal
from functools import lru_cache, reduce
from itertools import combinations, combinations_with_replacement, product, permutations
from operator import add, mul, sub

sys.setrecursionlimit(100000)
input = sys.stdin.readline


def read_int():
    return int(input())


def read_int_n():
    return list(map(int, input().split()))


def read_float():
    return float(input())


def read_float_n():
    return list(map(float, input().split()))


def read_str():
    return input().strip()


def read_str_n():
    return list(map(str, input().split()))


def error_print(*args):
    print(*args, file=sys.stderr)


def mt(f):
    import time

    def wrap(*args, **kwargs):
        s = time.time()
        ret = f(*args, **kwargs)
        e = time.time()

        error_print(e - s, 'sec')
        return ret

    return wrap


class Bisect:
    def __init__(self, func):
        self.__func = func

    def bisect_left(self, x, lo, hi):
        while lo < hi:
            mid = (lo+hi)//2
            if self.__func(mid) < x:
                lo = mid+1
            else:
                hi = mid
        return lo

    def bisect_right(self, x, lo, hi):
        while lo < hi:
            mid = (lo+hi)//2
            if x < self.__func(mid):
                hi = mid
            else:
                lo = mid+1
        return lo

@mt
def slv(N, S):
    t = defaultdict(list)
    for i, c in enumerate(S):
            t[c].append(i)
    def func(l):
        for j in range(N-l):
            for k in t[S[j]]:
                if k < j+l:
                    continue
                if k >= N-l+1:
                    continue
                for i in range(l):
                    if S[j+i] != S[k+i]:
                        break
                else:
                    return -l
        return 0

    b = Bisect(func)
    a = b.bisect_left(0, 0, N//2)
    if func(a) == 0 and a != 0:
        a -= 1
    return a


def main():
    N = read_int()
    S = read_str()
    print(slv(N, S))


    # N = 5000
    # for _ in range(1000):
    #     # S = ''.join(random.choices('abcdefghijklmnopqrstuwzxyz', k=N))
    #     S = ''.join(random.choices('abcdefghijklmnopqrstuwzxyz'[:random.randint(1, 26)], k=N))
    #     # S = ''.join(random.choices('a', k=N))
    #     # print(S)
    #     print(slv(N, S))


if __name__ == '__main__':
    main()


# Optimized solution
# -*- coding: utf-8 -*-
import bisect
import heapq
import math
import random
import sys
from collections import Counter, defaultdict, deque
from decimal import ROUND_CEILING, ROUND_HALF_UP, Decimal
from functools import lru_cache, reduce
from itertools import combinations, combinations_with_replacement, product, permutations
from operator import add, mul, sub

sys.setrecursionlimit(100000)
input = sys.stdin.readline


def read_int():
    return int(input())


def read_int_n():
    return list(map(int, input().split()))


def read_float():
    return float(input())


def read_float_n():
    return list(map(float, input().split()))


def read_str():
    return input().strip()


def read_str_n():
    return list(map(str, input().split()))


def error_print(*args):
    print(*args, file=sys.stderr)


def mt(f):
    import time

    def wrap(*args, **kwargs):
        s = time.time()
        ret = f(*args, **kwargs)
        e = time.time()

        error_print(e - s, 'sec')
        return ret

    return wrap

@mt
def slv(N, S):
    dp = [[0] * (N+1) for _ in range(N+1)]

    for i in range(N-1, -1, -1):
        for j in range(N-1, -1, -1):
            if S[i] == S[j]:
                dp[i][j] = dp[i+1][j+1] + 1
    
    ans = 0
    for i in range(N):
        for j in range(i+1, N):
            ans = max(ans, min(j-i, dp[i][j]))

    return ans


def main():
    N = read_int()
    S = read_str()
    print(slv(N, S))


if __name__ == '__main__':
    main()