#include <iostream> #include <map> #include <string> #include <vector> using namespace std; const int MAXN = 1e5 + 10; const int ALPHA = 26; struct PalindromicTree { int n, last, sz; int ans; struct Node { int len, sufflink, cnt; int nxt[ALPHA]; vector < int > adj; Node(){}; }; char str[MAXN]; Node tree[MAXN]; PalindromicTree(){}; void init() { str[0] = -1; tree[0].sufflink = 1; tree[0].len = 0; tree[1].sufflink = 1; tree[1].len = -1; sz = 2; n = 0; last = 1; } int get_par(int u) { while(str[n - tree[u].len - 1] != str[n]) { u = tree[u].sufflink; } return u; } void update(char c) { str[++n] = c; int letter = c - 'a'; int par = get_par(last); if(!tree[par].nxt[letter]) { int suff = get_par(tree[par].sufflink); tree[sz].len = tree[par].len + 2; tree[sz].sufflink = tree[suff].nxt[letter]; tree[sz].cnt = 1; tree[par].nxt[letter] = sz; tree[tree[sz].sufflink].adj.push_back(sz); sz++; } else { tree[tree[par].nxt[letter]].cnt++; } last = tree[par].nxt[letter]; } void build(string s) { for(int i = 0; i < s.size(); i++) { update(s[i]); } } void dfs(int u) { for(int v : tree[u].adj) { dfs(v); tree[u].cnt += tree[v].cnt; } ans = max(ans, tree[u].cnt * tree[u].len); } }; PalindromicTree paltree; string s; int main() { cin >> s; paltree.init(); paltree.build(s); paltree.dfs(0); cout << paltree.ans << endl; return 0; }