#include <bits/stdc++.h>
using namespace std;
struct Fast {
    Fast() {
        std::cin.tie(0);
        ios::sync_with_stdio(false);
        cout.precision(20);
    }
} fast;

/* define */
#define FOR(I, X, Y) for (long long(I) = (X); (I) < (Y); (I)++)
#define REP(I, X, Y) for (long long(I) = (Y)-1; (I) >= (X); (I)--)
#define ALL(X) (X).begin(), (X).end()
#define pb push_back
#define COUNT(V, X)                           \
    (upper_bound((V).begin(), (V).end(), X) - \
     lower_bound((V).begin(), (V).end(), X))
#define debug(x) cerr << #x << ':' << x << endl;
#define DEBUG(v)                             \
    {                                        \
        cerr << #v << ':';                   \
        for (auto xv : v) cerr << xv << ' '; \
        cerr << endl;                        \
    }
#define Yes(X) cout << (X ? "Yes" : "No") << endl;
#define YES(X) cout << (X ? "YES" : "NO") << endl;
#define ctoi(C) (C - '0')
#define pow2(x) ((long long)((long long)1 << x))

/* alias */
using ll = long long;
using ld = long double;
using vi = vector<int>;
using vii = vector<vector<int>>;
using vl = vector<long long>;
using vll = vector<vector<long long>>;
using pi = pair<int, int>;
using pl = pair<long long, long long>;
template <typename T>
using PQ = priority_queue<T>;
template <typename T>
using minPQ = priority_queue<T, vector<T>, greater<T>>;

/* const */
const long long dx[] = {1, 0, -1, 0};
const long long dy[] = {0, 1, 0, -1};
const long long dx8[] = {1, 1, 0, -1, -1, -1, 0, 1};
const long long dy8[] = {0, 1, 1, 1, 0, -1, -1, -1};
const long long dx9[] = {1, 1, 0, -1, -1, -1, 0, 1, 0};
const long long dy9[] = {0, 1, 1, 1, 0, -1, -1, -1, 0};
const int INF = 1000000007;
const long long LINF = 1000000000000000007;

/* func */
template <typename T1, typename T2>
inline bool chmin(T1 &a, const T2 &b) {
    if (a > b) a = b;
    return a > b;
}
template <typename T1, typename T2>
inline bool chmax(T1 &a, const T2 &b) {
    if (a < b) a = b;
    return a < b;
}
long long max(long long x, int y) {
    return max(x, (long long)y);
}
long long max(int x, long long y) {
    return max((long long)x, y);
}
long long min(long long x, int y) {
    return min(x, (long long)y);
}
long long min(int x, long long y) {
    return min((long long)x, y);
}

/* library */

// https://ei1333.github.io/luzhiled/snippets/string/rolling-hash.html
template <unsigned mod>
struct RollingHash {
    vector<unsigned> hashed, power;

    inline unsigned mul(unsigned a, unsigned b) const {
        unsigned long long x = (unsigned long long)a * b;
        unsigned xh = (unsigned)(x >> 32), xl = (unsigned)x, d, m;
        asm("divl %4; \n\t"
            : "=a"(d), "=d"(m)
            : "d"(xh), "a"(xl), "r"(mod));
        return m;
    }

    RollingHash(const string &s, unsigned base = 10007) {
        int sz = (int)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] = mul(power[i], base);
            hashed[i + 1] = mul(hashed[i], base) + s[i];
            if (hashed[i + 1] >= mod) hashed[i + 1] -= mod;
        }
    }

    unsigned get(int l, int r) const {
        unsigned ret = hashed[r] + mod - mul(hashed[l], power[r - l]);
        if (ret >= mod) ret -= mod;
        return ret;
    }

    unsigned connect(unsigned h1, int h2, int h2len) const {
        unsigned ret = mul(h1, power[h2len]) + h2;
        if (ret >= mod) ret -= mod;
        return ret;
    }

    int LCP(const RollingHash<mod> &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) / 2;
            if (get(l1, l1 + mid) == b.get(l2, l2 + mid))
                low = mid;
            else
                high = mid;
        }
        return (low);
    }
};

/* main */

string S;

bool check(ll imid, RollingHash<INF> &rh) {
    set<unsigned> s;
    if (imid == 0) return true;
    FOR(i, imid, S.size()) {
        s.insert(rh.get(i - imid, i));
        if (i + imid <= S.size()) {
            if (s.count(rh.get(i, i + imid))) {
                return true;
            }
        }
    }
    return false;
}

signed main() {
    int N;
    cin >> N;
    cin >> S;
    auto rh = RollingHash<INF>(S);
    ll imax = S.size();
    ll imin = 0;
    while (imax - imin > 1) {
        ll imid = (imax + imin) / 2;
        (check(imid, rh) ? imin : imax) = imid;
    }
    cout << imin << endl;
}


Measured memory_bytes: 512