#include <bits/stdc++.h>
#define range(i, l, r) for(int (i) = (l); (i) < (r); (i)++)
#define reversed_range(i, l, r) for (int (i) = (r) - 1; (i) >= l; (i)--)
using namespace std;
template <typename T>
using vec = vector<T>;
using lint = long long;
using ulint = unsigned long long;
using pint = pair<int, int>;
using plint = pair<lint, lint>;

template <typename S, typename T>
ostream& operator <<(ostream& os, pair<S, T> p) {
    os << "(";
    os << p.first << ", " << p.second;
    return os << ")";
}

template <typename T>
ostream& operator <<(ostream& os, vec<T> v) {
    os << "[";
    if (v.size() == 0) return os << "]";
    for (int i = 0; i < v.size() - 1; i++) {
        os << v.at(i) << ", ";
    }
    return os << v.at(v.size() - 1) << "]";
}

template <typename T>
ostream& operator <<(ostream& os, set<T>& s) {
    os << "{";
    if (s.begin() == s.end()) return os << "}";
    auto it_first_item = s.begin();
    cout << *it_first_item;
    for (auto it = ++it_first_item; it != s.end(); it++) {
        cout << ", " << *it;
    }
    return cout << "}";
}

template <typename T>
ostream& operator <<(ostream& os, unordered_set<T>& s) {
    os << "{";
    if (s.begin() == s.end()) return os << "}";
    auto it_first_item = s.begin();
    cout << *it_first_item;
    for (auto it = ++it_first_item; it != s.end(); it++) {
        cout << ", " << *it;
    }
    return cout << "}";
}

template <typename K, typename V>
ostream& operator <<(ostream& os, map<K, V> m) {
    os << "{";
    if (m.begin() == m.end()) return os << "}";
    auto it_first_item = m.begin();
    cout << it_first_item->first << ": " << it_first_item->second;
    for (auto it = ++it_first_item; it != m.end(); it++) {
        cout << ", " << it->first << ": " << it->second;
    }
    return os << "}";
}

template <typename K, typename V>
ostream& operator <<(ostream& os, unordered_map<K, V> m) {
    os << "{";
    if (m.begin() == m.end()) return os << "}";
    auto it_first_item = m.begin();
    cout << it_first_item->first << ": " << it_first_item->second;
    for (auto it = ++it_first_item; it != m.end(); it++) {
        cout << ", " << it->first << ": " << it->second;
    }
    return os << "}";
}

ulint pow(ulint num, lint e, ulint MOD) {
    ulint res = 1;
    ulint cur_num = num;
    while (e) {
        if (e & 1) {
            res *= cur_num;
            res %= MOD;
        }
        cur_num *= cur_num;
        cur_num %= MOD;
        e >>= 1;
    }
    return res;
}

int main() {
    cin.tie(0); cout.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    lint N; string S;
    cin >> N >> S;
    const ulint base = 29;
    auto this_len_possible = [&](lint len) {
        ulint hash = 0;
        ulint msb = pow(base, len - 1, ULLONG_MAX);
        range(i, 0, len) hash = hash * base + S.at(i);
        unordered_map<ulint, vec<lint>> hash_to_indices;
        hash_to_indices.emplace(hash, vec<lint>(1, 0));
        range(i, len, S.size()) {
            hash -= msb * S.at(i - len);
            hash = hash * base + S.at(i);
            lint start = i - len + 1;
            if (hash_to_indices.count(hash)) {
                for (const auto& index : hash_to_indices.at(hash)) {
                    if (index + len > start) continue;
                    range(j, 0, len) if (S.at(index + j) != S.at(start + j)) break;
                    return true;
                }
                hash_to_indices.at(hash).emplace_back(start);
            } else {
                hash_to_indices.emplace(hash, vec<lint>(1, start));
            }
        }
        return false;
    };

    lint lo = 0, hi = S.size() / 2 + 1;
    // [lo, hi)
    while (hi - lo > 1) {
        lint mid = (lo + hi) / 2;
        if (this_len_possible(mid)) lo = mid;
        else hi = mid;
    }
    cout << lo << "\n";
}

Measured memory_bytes: 800