#include <bits/stdc++.h>
using namespace std;
using LL = long long;

#define fs first
#define sc second

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }


// std::vector Declaration
template<typename T>
vector<T> make_v(size_t a) { return vector<T>(a); }
template<typename T,typename... Ts>
auto make_v(size_t a,Ts... ts) {
    return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));
}

// std::vector Initialization
template<typename T>
void fill_all(T& arr, const T& v) { arr = v; }
template<typename T, typename U>
void fill_all(T& arr, const U& v) { for (auto& i : arr) fill_all(i, v); }

// std::vector Debug
template<typename T>
ostream& operator<<(ostream& os, const vector<T>& v) {
    os << "[";
    bool a = 1;
    for (auto e : v) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "]";
    return os;
}

// std::deque Debug
template<typename T>
ostream& operator<<(ostream& os, const deque<T>& d) {
    os << "[";
    bool a = 1;
    for (auto e : d) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "]";
    return os;
}

// std::pair Debug
template<typename T, typename U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
    os << "(" << p.first << " " << p.second << ")";
    return os;
}

// std::set Debug
template<typename T>
ostream& operator<<(ostream& os, const set<T>& st) {
    os << "{";
    bool a = 1;
    for (auto e : st) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "}";
    return os;
}

// std::multiset Debug
template<typename T>
ostream& operator<<(ostream& os, const multiset<T>& st) {
    os << "{";
    bool a = 1;
    for (auto e : st) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "}";
    return os;
}

// std::map Debug
template<typename T, typename U>
ostream& operator<<(ostream& os, const map<T, U>& mp) {
    os << "{";
    bool a = 1;
    for (auto e : mp) {
        os << (a ? "" : " ");
        os << e.first << ":" << e.second;
        a = 0;
    }
    os << "}";
    return os;
}

// std::tuple Debug
template<int N, class Tuple>
void out(ostream& os, const Tuple& t){}
template<int N, class Tuple, class H, class ...Ts>
void out(ostream& os, const Tuple& t) {
    if (N) os << " ";
    os << get<N>(t);
    out<N+1,Tuple,Ts...>(os, t);
}
template<class ...Ts>
ostream& operator<<(ostream& os, const tuple<Ts...>& t) {
    os << "(";
    out<0,tuple<Ts...>,Ts...>(os, t);
    os << ")";
    return os;
}

// Debug
#define DUMP(x) cerr<<#x<<" = "<<(x)<<endl


struct edge { int to, cost; };
ostream& operator<<(ostream& os, const edge& e) {
    os << "(" << e.to << ", " << e.cost << ")";
    return os;
}

const LL LINF = 1LL<<60;
const int IINF = 1<<30;
const LL MOD = 1e9+7;

struct RollingHash {
    const int base = 9973;
    const vector<int> mod = {999999937LL, 1000000007LL};
    vector<int> s;
    vector<long long> hash[2], pow[2];

    // construct
    RollingHash(){}
    RollingHash(const vector<int> &cs) { init(cs); }
    void init(const vector<int> &cs) {
        s = cs;
        int n = s.size();
        for (int id = 0; id < 2; ++id) {
            hash[id].assign(n+1, 0);
            pow[id].assign(n+1, 1);
            for (int i = 0; i < n; ++i) {
                hash[id][i+1] = (hash[id][i] * base + s[i]) % mod[id];
                pow[id][i+1] = pow[id][i] * base % mod[id];
            }
        }
    }

    // get hash of s[l:r)
    inline long long get(int l, int r, int id = 0) const {
        long long res = hash[id][r] - hash[id][l] * pow[id][r-l] % mod[id];
        if (res < 0) res += mod[id];
        return res;
    }

    // get lcp length of s[a:] and s[b:]
    inline int getLCP(int a, int b) const {
        int len = min(s.size() - a, s.size() - b);
        int low = 0, high = len + 1;
        while (high - low > 1) {
            int mid = (low + high) / 2;
            if (get(a, a+mid, 0) != get(b, b+mid, 0) &&
                    get(a, a+mid, 1) != get(b, b+mid, 1)) high = mid;
            else low = mid;
        }
        return low;
    }

    // get lcp length of s[a:] and t[b:]
    inline int getLCP(const RollingHash &t, int a, int b) const {
        int len = min(s.size() - a, t.s.size() - b);
        int low = 0, high = len + 1;
        while (high - low > 1) {
            int mid = (low + high) / 2;
            if (get(a, a+mid, 0) != t.get(b, b+mid, 0) &&
                    get(a, a+mid, 1) != t.get(b, b+mid, 1)) high = mid;
            else low = mid;
        }
        return low;
    }
};

int main()
{
    int n; cin >> n;
    string s; cin >> s;

    vector<int> S(s.begin(), s.end());

    auto rh = RollingHash(S);

    int l = 0, r = n/2+1;
    while (r - l > 1) {
        int m = (l + r) / 2;

        bool flag = false;
        map<pair<int,int>, int> mp;

        for (int i = 0; i+m <= n; ++i) {
            auto hash = make_pair(
                    rh.get(i, i+m, 0), rh.get(i, i+m, 1));
            if (mp.find(hash) != mp.end() &&
                mp[hash] + m <= i) {
                flag = true;
                break;
            }
            if (mp.find(hash) == mp.end()) {
                mp[hash] = i;
            }
        }

        if (flag) {
            l = m;
        } else {
            r = m;
        }
    }

    cout << l << endl;

    return 0;
}


Measured memory_bytes: 896