Language: C++

#include <bits/stdc++.h>
using namespace std;
#ifndef ONLINE_JUDGE
	#include <boost/multiprecision/cpp_int.hpp>
	#include <boost/multiprecision/cpp_dec_float.hpp>
	using bll = boost::multiprecision::cpp_int;
	using bdouble = boost::multiprecision::cpp_dec_float_100;
#endif
#ifdef LOCAL_DEV
	void debug_impl() { std::cerr << std::endl; }
	template<typename Head, typename... Tail> void debug_impl(Head head, Tail... tail) { std::cerr << " " << head << (sizeof...(tail) ? "," : ""); debug_impl(tail...); }
	#define debug(...) { std::cerr << std::boolalpha << "(" << #__VA_ARGS__ << ") ="; debug_impl(__VA_ARGS__); std::cerr << std::noboolalpha; }
#else
	#define debug(...) {}
#endif
#ifdef LOCAL_TEST
	#define BOOST_STACKTRACE_USE_ADDR2LINE
	#define BOOST_STACKTRACE_ADDR2LINE_LOCATION /usr/local/opt/binutils/bin/addr2line
	#define _GNU_SOURCE
	#include <boost/stacktrace.hpp>
	template<typename T> class dvector : public std::vector<T> {
	public:
		dvector() : std::vector<T>() {}
		explicit dvector(size_t n, const T& value = T()) : std::vector<T>(n, value) {}
		dvector(const std::vector<T>& v) : std::vector<T>(v) {}
		dvector(const std::initializer_list<T> il) : std::vector<T>(il) {}
		dvector(const typename std::vector<T>::iterator first, const typename std::vector<T>::iterator last) : std::vector<T>(first, last) {}
		dvector(const std::string::iterator first, const std::string::iterator last) : std::vector<T>(first, last) {}
		T& operator[](size_t n) {
			try { return this->at(n); } catch (const std::exception& e) {
				std::cerr << boost::stacktrace::stacktrace() << std::endl; return this->at(n);
			}
		}
		const T& operator[](size_t n) const {
			try { return this->at(n); } catch (const std::exception& e) {
				std::cerr << boost::stacktrace::stacktrace() << std::endl; return this->at(n);
			}
		}
	};
	class dbool {
	private:
		bool boolvalue;
	public:
		dbool() : boolvalue(false) {}
		dbool(bool b) : boolvalue(b) {}
		dbool(const dbool &b) : boolvalue(b.boolvalue) {}
		operator bool&() { return boolvalue; }
		operator const bool&() const { return boolvalue; }
	};
	template<typename T> std::ostream& operator<<(std::ostream& s, const dvector<T>& v) {
		for (int i = 0, len = v.size(); i < len; ++i){ s << v[i]; if (i < len - 1) s << "\t"; } return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const dvector< dvector<T> >& vv) {
		for (int i = 0, len = vv.size(); i < len; ++i){ s << vv[i] << std::endl; } return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::set<T>& se) {
		s << "{ "; for (auto itr = se.begin(); itr != se.end(); ++itr){ s << (*itr) << "\t"; } s << "}"; return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::multiset<T>& se) {
		s << "{ "; for (auto itr = se.begin(); itr != se.end(); ++itr){ s << (*itr) << "\t"; } s << "}"; return s; }
	template<typename T1, typename T2> std::ostream& operator<<(std::ostream& s, const std::map<T1, T2>& m) {
		s << "{" << std::endl; for (auto itr = m.begin(); itr != m.end(); ++itr){ s << "\t" << (*itr).first << " : " << (*itr).second << std::endl; } s << "}"; return s; }
	template<typename T1, typename T2> std::ostream& operator<<(std::ostream& s, const std::pair<T1, T2>& p) { 
		return s << "(" << p.first << ", " << p.second << ")"; }
	#define vector dvector
	#define bool dbool
	class SIGFPE_exception : std::exception {};
	class SIGSEGV_exception : std::exception {};
	void catch_SIGFPE(int e) { std::cerr << boost::stacktrace::stacktrace() << std::endl; throw SIGFPE_exception();	}
	void catch_SIGSEGV(int e) { std::cerr << boost::stacktrace::stacktrace() << std::endl; throw SIGSEGV_exception(); }
	signed convertedmain();
	signed main() { signal(SIGFPE, catch_SIGFPE); signal(SIGSEGV, catch_SIGSEGV); return convertedmain(); }
	#define main() convertedmain()
#endif
//#define int long long
using ll = long long;
//constexpr int INF = 1e9;//INT_MAX=(1<<31)-1=2147483647
constexpr ll INF = (ll)1e18;//(1LL<<63)-1=9223372036854775807
constexpr ll MOD = (ll)1e9 + 7;
constexpr double EPS = 1e-9;
constexpr int dx[4] = {1, 0, -1, 0};
constexpr int dy[4] = {0, 1, 0, -1};
#define rep(i, n)   for(ll i=0, i##_length=(n); i< i##_length; ++i)
#define repeq(i, n) for(ll i=1, i##_length=(n); i<=i##_length; ++i)
#define rrep(i, n)   for(ll i=(n)-1; i>=0; --i)
#define rrepeq(i, n) for(ll i=(n)  ; i>=1; --i)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define uniq(v) (v).erase(unique((v).begin(), (v).end()), (v).end())
void p() { std::cout << '\n'; }
template<typename Head, typename... Tail> void p(Head head, Tail... tail) { std::cout << head << (sizeof...(tail) ? " " : ""); p(tail...); }
template<typename T> inline void pv(vector<T> &v) { for(ll i=0, N=v.size(); i<N; i++) std::cout << v[i] << " \n"[i==N-1]; }
template<typename T> inline T gcd(T a, T b) { return b ? gcd(b,a%b) : a; }
template<typename T> inline T lcm(T a, T b) { return a / gcd(a,  b) * b; }
template<typename T> inline bool chmax(T &a, T b) { return a < b && (a = b, true); }
template<typename T> inline bool chmin(T &a, T b) { return a > b && (a = b, true); }

/*-----8<-----template-----8<-----*/

/*
RollingHash(s, mod, base):= 文字列 s のハッシュテーブルを構築する。
get(l, r):= 区間 [l,r) のハッシュ値を求める。
connect(h1, h2, h2len):= ハッシュ値 h1 と, 長さ h2len のハッシュ値 h2 を結合する。
LCP(b, l1, r1, l2, r2):= 区間 [l1,r1) と, ハッシュテーブルが b からなる区間 [l2,r2) の文字列の最長共通接頭辞の長さを求める。
*/
template<typename rh_type>
class RollingHash {
public:
	rh_type mod;
	vector< rh_type > hashed, power;

	inline rh_type mul(rh_type a, rh_type b) const {
		return a * b % mod;
	}

	RollingHash(const string &s, rh_type mod = 2147483647, rh_type base = 524287) : mod(mod) {
		ll sz = (ll) s.size();
		hashed.assign(sz + 1, 0);
		power.assign(sz + 1, 0);
		power[0] = 1;
		for(ll 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;
		}
	}

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

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

	ll LCP(const RollingHash &b, ll l1, ll r1, ll l2, ll r2) {
		ll len = min(r1 - l1, r2 - l2);
		ll low = -1, high = len + 1;
		while(high - low > 1) {
			ll mid = (low + high) / 2;
			if(get(l1, l1 + mid) == b.get(l2, l2 + mid)) low = mid;
			else high = mid;
		}
		return (low);
	}
};

/*-----8<-----library-----8<-----*/

signed main() {
	//https://atcoder.jp/contests/abc141/tasks/abc141_e
	ll N;
	string S;
	cin>>N>>S;

	//using rh_type = boost::multiprecision::cpp_int;
	//using rh_type = __uint128_t;
	//using rh_type = unsigned long long;
	RollingHash<boost::multiprecision::cpp_int> rh(S);
	/*
	//強固にした定数版 __uint128_t以上必須です TLE注意
	constexpr ll rh_mod = 1e15 + 37;
	constexpr ll rh_base = 1e4 + 7;
	RollingHash<boost::multiprecision::cpp_int> rh(S, rh_mod, rh_base);
	*/
	/*
	//強固にした乱数版
	constexpr ll rh_mod = 1e15 + 37;
	std::random_device rnd;
	std::mt19937 mt(rnd());
	std::uniform_int_distribution<> rand_base(2, rh_mod-2);
	ll rh_base = rand_base(mt);
	RollingHash<boost::multiprecision::cpp_int> rh(S, rh_mod, rh_base);
	*/

	auto isOK = [&](ll len){
		map<ll, ll> m;
		for (ll i = 0; i + len <= N; ++i) {
			ll hash = rh.get(i, i+len);
			if (m.count(hash)) {
				if (i - m[hash] >= len) return true;
			} else {
				m[hash] = i;
			}
		}
		return false;
	};

	ll left = 0, right = N/2 + 1;
	while (right - left > 1) {
		ll mid = (left + right) / 2;
		if (isOK(mid)) left = mid;
		else right = mid;
	}
	
	cout<<left<<endl;
	return 0;
}


Compiler output:
a.cc:4:18: fatal error: boost/multiprecision/cpp_int.hpp: No such file or directory
    4 |         #include <boost/multiprecision/cpp_int.hpp>
      |                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.