#include <bits/stdc++.h>
using namespace std;
struct PalindromeNode {
PalindromeNode(int length, int suffixLink = 1)
: length(length), suffixLink(suffixLink), frequency(1) {
memset(nextNode, -1, sizeof nextNode);
}
int length;
int suffixLink;
int nextNode[26];
int frequency;
};
struct PalindromicTree {
PalindromicTree()
: NULL_PALINDROME(0), EMPTY_PALINDROME(1),
longestSuffixPalindrome(EMPTY_PALINDROME) {
nodes.push_back(PalindromeNode(-1, NULL_PALINDROME));
nodes.push_back(PalindromeNode(0, NULL_PALINDROME));
}
// return true of found a new palindrome
bool appendLetter(char letter) {
s += letter;
int index = (int)s.size() - 1;
int suffixLink = longestSuffixPalindrome;
// searching for longest palindrome in the new suffix
while (true) {
int R = index;
int L = R - nodes[suffixLink].length - 1;
if (L >= 0 && s[L] == s[R]) {
break;
}
else {
suffixLink = nodes[suffixLink].suffixLink;
}
}
// the palindrome already exists
if (nodes[suffixLink].nextNode[letter - 'a'] != -1) {
longestSuffixPalindrome = nodes[suffixLink].nextNode[letter - 'a'];
++nodes[longestSuffixPalindrome].frequency;
return false;
}
// found a new palindome
int newNode = fetchNode(nodes[suffixLink].length + 2);
nodes[suffixLink].nextNode[letter - 'a'] = newNode;
longestSuffixPalindrome = newNode;
// finding the suffix link of the new node
if (nodes[newNode].length == 1) {
nodes[newNode].suffixLink = EMPTY_PALINDROME;
}
else {
while (true) {
suffixLink = nodes[suffixLink].suffixLink;
int R = index;
int L = R - nodes[suffixLink].length - 1;
if (L >= 0 && s[L] == s[R]) {
nodes[newNode].suffixLink = nodes[suffixLink].nextNode[letter - 'a'];
break;
}
}
}
return true;
}
// maintain the frequency of each palindome
void propagate() {
for (const PalindromeNode& palindome : nodes) {
int parent = palindome.suffixLink;
nodes[parent].frequency += palindome.frequency;
}
}
// return the index of the new fetched node
int fetchNode(int length) {
nodes.push_back(PalindromeNode(length));
return (int)nodes.size() - 1;
}
// return the index of the new fetched node
int fetchNode(int length, int suffixLink) {
nodes.push_back(PalindromeNode(length, suffixLink));
return (int)nodes.size() - 1;
}
const int NULL_PALINDROME; // palindrome of length -1
const int EMPTY_PALINDROME; // palindrome of length 0
int longestSuffixPalindrome;
vector<PalindromeNode> nodes;
string s;
};
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
string s;
cin >> s;
PalindromicTree tree;
for (char letter : s) {
tree.appendLetter(letter);
}
tree.propagate();
long long maxOccurrenceValue = LLONG_MIN;
for (PalindromeNode& palindrome : tree.nodes) {
long long occurrenceValue = 1LL * palindrome.length * palindrome.frequency;
maxOccurrenceValue = max(maxOccurrenceValue, occurrenceValue);
}
cout << maxOccurrenceValue;
return 0;
}
