//  ____            _                  _                       _       _
// |  _ \ _   _ ___| |_    ___ _ __   | |_ ___ _ __ ___  _ __ | | __ _| |_ ___
// | |_) | | | / __| __|  / __| '_ \  | __/ _ \ '_ ` _ \| '_ \| |/ _` | __/ _ \
// |  _ <| |_| \__ \ |_  | (__| |_) | | ||  __/ | | | | | |_) | | (_| | ||  __/
// |_| \_\\__,_|___/\__|  \___| .__/___\__\___|_| |_| |_| .__/|_|\__,_|\__\___|
//                            |_| |_____|               |_|

//https://github.com/manta1130/Competitive_Programming_Template_Rust

#[macro_use]
mod input {

    use std;
    use std::io;

    const SPLIT_DELIMITER: char = ' ';

    #[macro_export]
    #[allow(unused_macros)]
    macro_rules! input {
    ( $($x:expr ),*) => {
        {
            let temp_str = input_line_str();
            let mut split_result_iter = temp_str.split_whitespace();
                $(
                let buf_split_result = split_result_iter.next();
                let buf_split_result = buf_split_result.unwrap();
                    ($x) = buf_split_result.parse().unwrap();
                )*
        }
    };
}

    #[allow(dead_code)]
    pub fn input_line_str() -> String {
        let mut s = String::new();
        io::stdin().read_line(&mut s).unwrap();
        s.trim().to_string()
    }

    #[allow(dead_code)]
    pub fn p<T>(t: T)
    where
        T: std::fmt::Display,
    {
        println!("{}", t);
    }

    #[allow(dead_code)]
    pub fn input_vector2d<T>(line: usize) -> Vec<Vec<T>>
    where
        T: std::str::FromStr,
    {
        let mut v: Vec<Vec<T>> = Vec::new();

        for _ in 0..line {
            let vec_line = input_vector();
            v.push(vec_line);
        }
        v
    }

    #[allow(dead_code)]
    pub fn input_vector<T>() -> Vec<T>
    where
        T: std::str::FromStr,
    {
        let mut v: Vec<T> = Vec::new();

        let s = input_line_str();
        let split_result = s.split(SPLIT_DELIMITER);
        for z in split_result {
            let buf = match z.parse() {
                Ok(r) => r,
                Err(_) => panic!("Parse Error"),
            };
            v.push(buf);
        }
        v
    }

    #[allow(dead_code)]
    pub fn input_vector_row<T>(n: usize) -> Vec<T>
    where
        T: std::str::FromStr,
    {
        let mut v = Vec::with_capacity(n);
        for _ in 0..n {
            let buf = match input_line_str().parse() {
                Ok(r) => r,
                Err(_) => panic!("Parse Error"),
            };
            v.push(buf);
        }
        v
    }

    pub trait ToCharVec {
        fn to_charvec(&self) -> Vec<char>;
    }

    impl ToCharVec for String {
        fn to_charvec(&self) -> Vec<char> {
            self.to_string().chars().collect::<Vec<_>>()
        }
    }
}

mod  rolling_hash{

use std::num::Wrapping;

type ValueType = u64;

pub struct RollingHash {
    base: ValueType,
    v: Vec<ValueType>,
    pow: Vec<ValueType>,
}

///ローリングハッシュ
impl RollingHash {
    ///ローリングハッシュを計算する。
    ///
    /// base:基数
    pub fn calc(input_str: &str, base: ValueType) -> RollingHash {
        let mut v = vec![0];
        let mut pow = vec![1];
        let mut pow_buf = base;
        let mut hash: ValueType = 0;

        for _ in 0..input_str.len() {
            pow.push(pow_buf);
            pow_buf = (Wrapping(pow_buf) * Wrapping(base)).0;
        }

        for c in input_str.as_bytes() {
            hash = (Wrapping(base) * Wrapping(hash)).0;
            hash = (Wrapping(hash) + Wrapping(*c as ValueType)).0;
            v.push(hash);
        }
        RollingHash {
            base: base,
            v: v,
            pow: pow,
        }
    }

    ///[from:to)のローリングハッシュを求める。
    pub fn get(&self, from: usize, to: usize) -> ValueType {
        let buf = (Wrapping(self.v[from]) * Wrapping(self.pow[to - from])).0;
        (Wrapping(self.v[to]) - Wrapping(buf)).0
    }
}
}

use input::*;
use rolling_hash::*;

use std::collections::HashMap;

fn main() {
    let n: usize;
    input!(n);
    let s = input_line_str();
    let hash1 = RollingHash::calc(&s, 1_000_000_007);
    let hash2 = RollingHash::calc(&s, 9007199254740997);

    let mut ok = 0;
    let mut ng = n;
    while ng - ok != 1 {
        let mid = (ok + ng) / 2;
        let mut map = HashMap::new();
        let mut map2 = HashMap::new();
        let mut flag = false;
        for i in 0..n {
            if i + mid > n {
                break;
            }
            if map.contains_key(&hash1.get(i, i + mid)) && map2.contains_key(&hash2.get(i, i + mid))
            {
                if map[&hash1.get(i, i + mid)] + mid <= i && map2[&hash2.get(i, i + mid)] + mid <= i {
                    flag = true;
                }
            } else {
                map.insert(hash1.get(i, i + mid), i);
                map2.insert(hash2.get(i, i + mid), i);
            }
            if flag {
                break;
            }
        }
        if flag {
            ok = mid;
        } else {
            ng = mid;
        }
    }
    p(ok);
}


Measured memory_bytes: 4352