### BUGGY CODE ###

# -*- 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):
    if N < 27:
        if Counter(S).most_common(1)[0][1] == 1:
            return 0

    ans = 0
    t = defaultdict(list)
    for i in range(N-1):
        t[S[i:i+1]].append(i)

    def eq(i, j):
        L = min(N-j, j-i)
        for k in range(L):
            if S[i+k] != S[j+k]:
                return k
        return L
    
    ans = 1
    for c in t:
        idx = t[c]
        for i in range(len(idx)):
            for j in range(i+1, len(idx)):
                if idx[j] - idx[i] > ans and N - idx[j] > ans:
                    ans = max(ans, eq(idx[i], idx[j]))
    return ans


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('abcde', k=N))
    #     # S = ''.join(random.choices('a', k=N))
    #     # print(S)
    #     print(slv(N, S))


if __name__ == '__main__':
    main()


### FIXED CODE ###

# -*- 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()