Language: C++

// May this submission get accepted!

#pragma GCC optimize ("O3")
#pragma GCC target ("tune=native")
#pragma GCC target ("avx")

#include <bits/stdc++.h>

// 汎用マクロ
#define ALL_OF(x) (x).begin(), (x).end()
#define REP(i,n) for (long long i=0, i##_len=(n); i<i##_len; i++)
#define RANGE(i,is,ie) for (long long i=(is), i##_end=(ie); i<=i##_end; i++)
#define DSRNG(i,is,ie) for (long long i=(is), i##_end=(ie); i>=i##_end; i--)
#define UNIQUE(v) do { sort((v).begin(), (v).end()); (v).erase(unique((v).begin(), (v).end()), (v).end()); } while (false)
template<class T> bool chmax(T &a, const T &b) {if (a < b) {a = b; return true;} return false; }
template<class T> bool chmin(T &a, const T &b) {if (a > b) {a = b; return true;} return false; }
#define INF 0x7FFFFFFF
#define LINF 0x7FFFFFFFFFFFFFFFLL
#define Yes(q) ((q) ? "Yes" : "No")
#define YES(q) ((q) ? "YES" : "NO")
#define Possible(q) ((q) ? "Possible" : "Impossible")
#define POSSIBLE(q) ((q) ? "POSSIBLE" : "IMPOSSIBLE")
#define DUMP(q) cerr << "[DEBUG] " #q ": " << (q) << " at " __FILE__ ":" << __LINE__ << endl
#define DUMPALL(q) do { cerr << "[DEBUG] " #q ": ["; REP(i, (q).size()) { cerr << (q)[i] << (i == i_len-1 ? "" : ", "); } cerr << "] at " __FILE__ ":" << __LINE__ << endl; } while (false)
template<class T> T gcd(const T &a, const T &b) { return a < b ? gcd(b, a) : b ? gcd(b, a % b) : a; }
template<class T> T lcm(const T &a, const T &b) { return a / gcd(a, b) * b; }

// gcc拡張マクロ
#define popcount __builtin_popcount
#define popcountll __builtin_popcountll

// エイリアス
#define DANCE_ long
#define ROBOT_ unsigned
#define HUMAN_ signed
#define CHOKUDAI_ const
using  ll = DANCE_ HUMAN_ DANCE_;
using ull = DANCE_ ROBOT_ DANCE_;
using cll = DANCE_ DANCE_ CHOKUDAI_;
using  ld = long double;
using namespace std;

// モジュール
template <class RandomAccessIterator>
vector<ll> common_prefix(RandomAccessIterator first, RandomAccessIterator last) {
    const size_t sz = last - first;
    vector<ll> prefix(sz, 0);
    for (size_t i = 1, j = 0; i < sz; i++) {
        if (i + prefix[i-j] < j + prefix[j]) {
            prefix[i] = prefix[i-j];
        } else {
            ll k = max(0LL, j + prefix[j] - i);
            while (i + k < sz && *(first + k) == *(first + (i+k))) k++;
            prefix[i] = k;
            j = i;
        }
    }
    prefix[0] = sz;
    return prefix;
}

// 処理内容
int main() {

    ll n; cin >> n;
    string s; cin >> s;
    
    ll ans = 0;
    REP(k, n) {
        vector<ll> prefix = common_prefix(s.begin() + k, s.end());
        REP(i, prefix.size()) chmin(prefix[i], i);
        chmax(ans, *max_element(ALL_OF(prefix)));
    }
    cout << ans << endl;
    
}

Compiler output:
a.cc: In function 'std::vector<long long int> common_prefix(RandomAccessIterator, RandomAccessIterator)':
a.cc:52:23: error: no matching function for call to 'max(long long int, long long unsigned int)'
   52 |             ll k = max(0LL, j + prefix[j] - i);
      |                    ~~~^~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:7:
/usr/include/c++/14/bits/stl_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:52:23: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and 'long long unsigned int')
   52 |             ll k = max(0LL, j + prefix[j] - i);
      |                    ~~~^~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61:
/usr/include/c++/14/bits/stl_algo.h:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:52:23: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   52 |             ll k = max(0LL, j + prefix[j] - i);
      |                    ~~~^~~~~~~~~~~~~~~~~~~~~~~~