### BUGGY CODE ###

# -*- coding: utf-8 -*-

import sys

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

N = INT()
S = input()

def bisearch_max(mn, mx, func):
    """ 条件を満たす最大値を見つける二分探索 """

    ok = mn
    ng = mx
    while ok+1 < ng:
        mid = (ok+ng) // 2
        if func(mid):
            # 上を探しに行く
            ok = mid
        else:
            # 下を探しに行く
            ng = mid
    return ok

def calc(m):
    for i in range(N-m*2+1):
        a = S[i:i+m]
        b = S[i+m:]
        if b.count(a):
            return True
    return False

print(bisearch_max(0, N, calc))


### FIXED CODE ###

# -*- coding: utf-8 -*-

import sys

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

N = INT()
S = input()

def bisearch_max(mn, mx, func):
    """ 条件を満たす最大値を見つける二分探索 """

    ok = mn
    ng = mx
    while ok+1 < ng:
        mid = (ok+ng) // 2
        if func(mid):
            # 上を探しに行く
            ok = mid
        else:
            # 下を探しに行く
            ng = mid
    return ok

class RollingHash:

    MOD = 2 ** 64
    b = 10 ** 8 + 7

    def __init__(self, S):
        # 各文字を数値に変換しておく
        S = [ord(s)-97 for s in S]

        self.len = len(S)
        self.pow = [1] * (self.len+1)
        for i in range(self.len):
            self.pow[i+1] = self.pow[i] * self.b
            self.pow[i+1] %= self.MOD
        # ハッシュの生成
        self.hash = [0] * (self.len+1)
        for i in range(self.len):
            self.hash[i+1] = self.hash[i] * self.b + S[i]
            self.hash[i+1] %= self.MOD
    
    # 区間[i,j)のハッシュ値を取得
    def get(self, l, r):
        return (self.hash[r] - self.hash[l] * self.pow[r-l]) % self.MOD

def calc(m):
    A = {}
    for i in range(N-m+1):
        a_hash = rh.get(i, i+m)
        if a_hash in A:
            # a_hashが2回目以降に出現したindex
            j = A[a_hash]
            # iとjがm以上離れているかどうか
            if i-j >= m:
                return True
        else:
            # a_hashが最初に出現したindex
            A[a_hash] = i
    return False

rh = RollingHash(S)
print(bisearch_max(0, N, calc))