#define ATCODER #define _USE_MATH_DEFINES #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; using ll = long long; using ld = long double; using pll = pair; using pdd = pair; //template using pq = priority_queue, greater>; #define FOR(i, a, b) for(ll i=(a); i<(b);i++) #define REP(i, n) for(ll i=0; i<(n);i++) #define ROF(i, a, b) for(ll i=(b-1); i>=(a);i--) #define PER(i, n) for(ll i=n-1; i>=0;i--) #define REPREP(i,j,a,b) for(ll i=0;i > #define VV2(type,n,m,val) vector< vector > val;val.resize(n);for(ll i;i #define VEC(type,n,val) vector val;val.resize(n) #define VL vector #define VVL vector< vector > #define VP vector< pair > #define SZ size() #define all(i) begin(i),end(i) #define SORT(i) sort(all(i)) #define BITI(i) (1<>i) & 1) != 0) #define ALLBIT(n) (ll(1)<v?v:n #define MP(a,b) make_pair(a,b) #define DET2(x1,y1,x2,y2) x1*y2-x2*y1 #define DET3(x1,y1,z1,x2,y2,z2,x3,y3,z3) x1*y2*z3+x2*y3*z1+x3*y1*z2-z1*y2*x3-z2*y3*x1-z3*y1*x2 #define INC(a) for(auto& v:a)v++; #define DEC(a) for(auto& v:a)v--; #define SQU(x) (x)*(x) #define L0 ll(0) #ifdef ATCODER #include using namespace atcoder; using mint = modint1000000007; using mint2 = modint998244353; #endif template vector read(size_t n) { vector ts(n); for (size_t i = 0; i < n; i++) cin >> ts[i]; return ts; } template void read_tuple_impl(TV&) {} template void read_tuple_impl(TV& ts) { get(ts).emplace_back(*(istream_iterator(cin))); read_tuple_impl(ts); } template decltype(auto) read_tuple(size_t n) { tuple...> ts; for (size_t i = 0; i < n; i++) read_tuple_impl(ts); return ts; } using val = pair; using func = ll; val op(val a, val b) { return MP(a.first + b.first, a.second + b.second); } val e() { return MP(0, 0); } val mp(func f, val a) { return MP(a.first + f * a.second, a.second); } func comp(func f, func g) { return f + g; } func id() { return 0; } ll di[4] = { 1,0,-1,0 }; ll dj[4] = { 0,1,0,-1 }; ll si[4] = { 0,3,3,0 }; ll sj[4] = { 0,0,3,3 }; //ll di[4] = { -1,-1,1,1 }; //ll dj[4] = { -1,1,-1,1 }; ll di8[8] = { 0,-1,-1,-1,0,1,1,1 }; ll dj8[8] = { -1,-1,0,1,1,1,0,-1 }; struct PalindromicTree { // // private: struct node { map link; int suffix_link; ll len; ll count; }; vector c; string s; int active_idx; node* create_node() { c.emplace_back(); node* ret = &c.back(); ret->count = 0; return ret; } // this->s の状態に依存する int find_prev_palindrome_idx(int node_id) { const int pos = int(s.size()) - 1; while (true) { const int opposite_side_idx = pos - 1 - c[node_id].len; if (opposite_side_idx >= 0 && s[opposite_side_idx] == s.back()) break; node_id = c[node_id].suffix_link; // 次の回文に移動 } return node_id; } bool debug_id2string_dfs(int v, int id, vector& charas) { if (v == id) return true; for (auto kv : c[v].link) { if (debug_id2string_dfs(kv.second, id, charas)) { charas.push_back(kv.first); return true; } } return false; } public: PalindromicTree() { node* size_m1 = create_node(); // 長さ-1のノードを作成 size_m1->suffix_link = 0; // -1 の親suffixは自分自身 size_m1->len = -1; node* size_0 = create_node(); // 長さ0のノードを作成 size_0->suffix_link = 0; // 親は長さ-1のノード size_0->len = 0; active_idx = 0; } int get_active_idx() const { return active_idx; } node* get_node(int id) { return &c[id]; } void add(char ch) { s.push_back(ch); // ch + [A] + ch が回文となるものを探す const int a = find_prev_palindrome_idx(active_idx); //新しいノードへのリンクが発生するか試す const auto inserted_result = c[a].link.insert(make_pair(ch, int(c.size()))); active_idx = inserted_result.first->second; // insertの成否に関わらず、iteratorが指す先は新しい回文のindex if (!inserted_result.second) { c[active_idx].count++; // その回文が現れた回数が増加 return; // 既にリンクが存在したので、新しいノードを作る必要がない } // 実際に新しいノードを作成 node* nnode = create_node(); nnode->count = 1; nnode->len = c[a].len + 2; // ch + [A] + ch だから、長さは len(A) + 2 // suffix_linkの設定 if (nnode->len == 1) { // この時だけsuffix_linkはsize 0に伸ばす nnode->suffix_link = 1; } else { // ch + [B] + ch が回文になるものを探す。ただし長さはaより小さいもの const int b = find_prev_palindrome_idx(c[a].suffix_link); nnode->suffix_link = c[b].link[ch]; } } //各文字列が何回現れるか計算する // O(n) vector build_frequency() { vector frequency(c.size()); //常に親ノードのid < 子ノードのidが成り立つので、idを大きい順から回せばよい for (int i = int(c.size()) - 1; i > 0; i--) { frequency[i] += c[i].count; frequency[c[i].suffix_link] += frequency[i]; } return frequency; } }; VL ans; vector freq; void solve2(PalindromicTree& pt, ll idx) { if (ans[idx] != -1) { return; } auto no = pt.get_node(idx); ll p = no->suffix_link; if (p == idx) { ans[idx] = 0; return; } solve2(pt, p); ans[idx] = ans[p] + freq[idx] * no->len; } void solve() { string s; cin >> s; PalindromicTree pt; for (auto c : s) { pt.add(c); } freq = pt.build_frequency(); ll siz = pt.c.size(); ans.assign(siz, -1); REP(i, siz) { if (ans[i] != -1) continue; solve2(pt, i); } cout << *max_element(all(ans)); return; } int main() { ll t = 1; //cin >> t; while (t--) { solve(); } return 0; }