#include <cstdio>
#include <vector>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;

int n;
const int MAX_LEN = 200010;
const int P = 10007;
char str[MAX_LEN];
int exponent[MAX_LEN];

void create_exponent(int n) {
    exponent[0] = 1;
    for (int i = 1; i < n; i++) {
        exponent[i] = (long long)(P) * exponent[i - 1];
    }
}

class Hash {
    vector<long long> v;
public:
    Hash() {}
    void initialize(char* str) {
        this->v.resize(n, 0);
        this->v[0] = str[0];
        for (int i = 1; i < n; i++) {
            this->v[i] = this->v[i-1] * P + str[i];
        }
    }
    int get_hash(int loc, int len) {
        int h;
        if (loc == 0) {
            h = this->v[len - 1];
        } else {
            h = (this->v[loc + len - 1] - (this->v[loc - 1] * exponent[len]));
        }
        return h;
    }
};

Hash hc;

bool find_length(int mid) {
    int hash_code[n - mid + 1];
    for (int i = 0; i < n - mid + 1; i++) {
        hash_code[i] = hc.get_hash(i, mid);
    }
    sort(hash_code, hash_code + n - mid + 1);
    for (int i = 0; i < n - mid; i++)
        if (hash_code[i] == hash_code[i + 1])
            return true;
    return false;
}

int main() {
    scanf("%d", &n);
    scanf("%s", &str);
    hc.initialize(str);

    create_exponent(MAX_LEN);

    int s = 0, e = n;
    int mid;

    while (s + 1 < e) {
        mid = (s + e) / 2;
        if (find_length(mid)) {
            s = mid;
        } else {
            e = mid;
        }
    }
    printf("%d\n", s);

    return 0;
}