### BUGGY CODE ###

#!/usr/bin/env python3
ans=0
n=int(input())
s=input()
class RollingHash():
    BASE1 = 1007
    BASE2 = 2009
    MOD1 = 1000000007
    MOD2 = 1000000009
 
    def __init__(self, s, opt=2):
        self.n = len(s)
        self.opt = opt
        self.hash1 = [0] * (self.n + 1)
        self.power1 = [1] * (self.n + 1)
        if opt == 2:
            self.hash2 = [0] * (self.n + 1)
            self.power2 = [1] * (self.n + 1)
        for i, e in enumerate(s):
            self.hash1[i + 1] = (self.hash1[i] * self.__class__.BASE1 + ord(e)) % self.__class__.MOD1
            self.power1[i + 1] = (self.power1[i] * self.__class__.BASE1) % self.__class__.MOD1
            if opt == 2:
                self.hash2[i + 1] = (self.hash2[i] * self.__class__.BASE2 + ord(e)) % self.__class__.MOD2
                self.power2[i + 1] = (self.power2[i] * self.__class__.BASE2) % self.__class__.MOD2
 
    def get(self, l: int, r: int):
        res1 = self.hash1[r] - self.hash1[l] * self.power1[r - l] % self.__class__.MOD1
        if(res1 < 0):
            res1 += self.__class__.MOD1
        if self.opt == 2:
            res2 = self.hash2[r] - self.hash2[l] * self.power2[r - l] % self.__class__.MOD2
            if(res2 < 0):
                res2 += self.__class__.MOD2
        return (res1, res2) if self.opt == 2 else res1

rh=RollingHash(s)
for i in range(n-2):
    for le in range(1,n//2+1):
        for j in range(i+le,n-le+1):
            if rh.get(i,i+le)==rh.get(j,j+le):
                ans=max(ans,le)
print(ans)


### FIXED CODE ###

N=int(input())
S=input()

class RollingHash():
    BASE1 = 1007
    BASE2 = 2009
    MOD1 = 1000000007
    MOD2 = 1000000009
 
    def __init__(self, s, opt=2):
        self.n = len(s)
        self.opt = opt
        self.hash1 = [0] * (self.n + 1)
        self.power1 = [1] * (self.n + 1)
        if opt == 2:
            self.hash2 = [0] * (self.n + 1)
            self.power2 = [1] * (self.n + 1)
        for i, e in enumerate(s):
            self.hash1[i + 1] = (self.hash1[i] * self.__class__.BASE1 + ord(e)) % self.__class__.MOD1
            self.power1[i + 1] = (self.power1[i] * self.__class__.BASE1) % self.__class__.MOD1
            if opt == 2:
                self.hash2[i + 1] = (self.hash2[i] * self.__class__.BASE2 + ord(e)) % self.__class__.MOD2
                self.power2[i + 1] = (self.power2[i] * self.__class__.BASE2) % self.__class__.MOD2
 
    def get(self, l: int, r: int):
        res1 = self.hash1[r] - self.hash1[l] * self.power1[r - l] % self.__class__.MOD1
        if(res1 < 0):
            res1 += self.__class__.MOD1
        if self.opt == 2:
            res2 = self.hash2[r] - self.hash2[l] * self.power2[r - l] % self.__class__.MOD2
            if(res2 < 0):
                res2 += self.__class__.MOD2
        return (res1, res2) if self.opt == 2 else res1


    
rh = RollingHash(S, opt=1)

def check(n: int):
    d = dict()
    for i in range(N - n + 1):
        p = rh.get(i, i + n)
        if p in d.keys():
            if(i - d[p] >= n):
                return True
        else:
            d[p] = i
    return False
    
ok, ng = 0, N // 2 + 1
while ng - ok > 1:
    mid = (ok + ng) // 2
    if check(mid):
        ok = mid
    else:
        ng = mid
print(ok)