#include <bits/stdc++.h>
using namespace std;
using lint = long long;
const lint mod = 1e9 + 7;
#define all(x) (x).begin(), (x).end()
#define bitcount(n) __builtin_popcountl((lint)(n))
#define fcout cout << fixed << setprecision(15)
#define highest(x) (63 - __builtin_clzl(x))
template<class T> inline void YES(T condition){ if(condition) cout << "YES" << endl; else cout << "NO" << endl; }
template<class T> inline void Yes(T condition){ if(condition) cout << "Yes" << endl; else cout << "No" << endl; }
template<class T = string, class U = char>int character_count(T text, U character){ int ans = 0; for(U i: text){ ans += (i == character); } return ans; }
lint power(lint base, lint exponent, lint module){ if(exponent % 2){ return power(base, exponent - 1, module) * base % module; }else if(exponent){ lint root_ans = power(base, exponent / 2, module); return root_ans * root_ans % module; }else{ return 1; }}
struct position{ int y, x; }; position mv[4] = {{0, -1}, {1, 0}, {0, 1}, {-1, 0}}; // double euclidean(position first, position second){ return sqrt((second.x - first.x) * (second.x - first.x) + (second.y - first.y) * (second.y - first.y)); }
template<class T, class U> string to_string(pair<T, U> x){ return to_string(x.first) + "," + to_string(x.second); } string to_string(string x){ return x; }
template<class itr> void array_output(itr start, itr goal){ string ans; for(auto i = start; i != goal; i++) ans += to_string(*i) + " "; if(!ans.empty()) ans.pop_back(); cout << ans << endl; }
template<class itr> void cins(itr first, itr last){ for(auto i = first; i != last; i++){ cin >> (*i); } }
template<class T> T gcd(T a, T b){ if(a && b){ return gcd(min(a, b), max(a, b) % min(a, b)); }else{ return a; }} template<class T> T lcm(T a, T b){ return a / gcd(a, b) * b; }
struct combination{ vector<lint> fact, inv; combination(int sz) : fact(sz + 1), inv(sz + 1){ fact[0] = 1; for(int i = 1; i <= sz; i++){ fact[i] = fact[i - 1] * i % mod; } inv[sz] = power(fact[sz], mod - 2, mod); for(int i = sz - 1; i >= 0; i--){ inv[i] = inv[i + 1] * (i + 1) % mod; } } lint C(int p, int q) const{ if(q < 0 || p < q) return 0; return (fact[p] * inv[q] % mod * inv[p - q] % mod); } };
template<class itr> bool next_sequence(itr first, itr last, int max_bound){ itr now = last; while(now != first){ now--; (*now)++; if((*now) == max_bound){ (*now) = 0; }else{ return true; } } return false; }

using ll = __int128_t;

ll _base = 100000000000000021ll, _mod = 999999999999999967ll;

struct RollingHash
{
    vector< ll > hashed, power;
    RollingHash(const string& s)
    {
        int sz = s.size();
        hashed.assign(sz + 1, 0);
        power.assign(sz + 1, 0);
        
        power[0] = 1;
        for(int i = 0; i < sz; i++) {
            power[i + 1] = power[i] * _base % _mod;
        }
        for(int i = 0; i < sz; i++) {
            hashed[i + 1] = (hashed[i] + s[i]) * _base % _mod;
        }
    }
    ll get(int l, int r) // [l, r)
    {
        return((hashed[r] - hashed[l] * power[r - l] % _mod + _mod) % _mod);
    }
    ll connect(int h1, int h2, int h2len)
    {
        return(h1 * power[h2len] + h2);
    }
    int LCP(RollingHash& b, int l1, int r1, int l2, int r2)
    {
        int len = min(r1 - l1, r2 - l2);
        int low = -1, high = len + 1;
        while(high - low > 1) {
            int mid = (low + high) >> 1;
            if(get(l1, l1 + mid) == b.get(l2, l2 + mid)) low = mid;
            else high = mid;
        }
        return(low);
    }
};

int main(){
    int N;
    cin >> N;
    string S;
    cin >> S;
    RollingHash str(S);
    for(int i = N / 2; i >= 1; i--){
        vector<lint> nums;
        for(int j = 0; j <= N - i; j++){
            lint num = str.get(j, j + i);
            nums.push_back(num);
        }
        unordered_set<lint> nums2;
        for(int j = i; j <= N - i; j++){
            nums2.insert(nums[j - i]);
            if(nums2.find(nums[j]) != nums2.end()){
                cout << i << endl;
                return 0;
            }
        }
    }
    cout << 0 << endl;
}

Measured memory_bytes: 744