#include <iostream>
#include <iomanip>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <list>
#include <stack>
#include <queue>
#include <bitset>
#include <numeric>
#include <cassert>
#include <array>
#include <memory>
#ifdef DEBUG
#include "./Lib/debug.hpp"
#include "./Lib/Timer.hpp"
#include "./Lib/sample.hpp"
#else
#define dump(...)
#endif

/* (=＾o＾=) */
#define int ll

/* macro */
#define FOR(i, b, e) for(ll i = (ll)(b); i < (ll)(e); ++i)
#define RFOR(i, b, e) for(ll i = (ll)(e-1); i >= (ll)(b); --i)
#define REP(i, n) FOR(i, 0, n)
#define RREP(i, n) RFOR(i, 0, n)
#define REPC(x,c) for(const auto& x:(c))
#define REPI2(it,b,e) for(auto it = (b); it != (e); ++it)
#define REPI(it,c) REPI2(it, (c).begin(), (c).end())
#define RREPI(it,c) REPI2(it, (c).rbegin(), (c).rend())
#define REPI_ERACE2(it, b, e) for(auto it = (b); it != (e);)
#define REPI_ERACE(it, c) REPI_ERACE2(it, (c).begin(), (c).end())
#define ALL(x) (x).begin(),(x).end()
#define cauto const auto&
/* macro func */
template<class T>
inline auto sort(T& t) { std::sort(ALL(t)); }
template<class T>
inline auto rsort(T& t) { std::sort((t).rbegin(), (t).rend()); }
template<class T>
inline auto unique(T& t) { (t).erase(unique((t).begin(), (t).end()), (t).end()); }
template<class T, class S>
inline auto chmax(T& t, const S& s) { if (s > t) { t = s; return true; } return false; }
template<class T, class S>
inline auto chmaxE(T& t, const S& s) { if (s >= t) { t = s; return true; } return false; }
template<class T, class S>
inline auto chmin(T& t, const S& s) { if (s < t) { t = s; return true; } return false; }
inline auto BR() { std::cout << "\n"; }

/* type define */
using ll = long long;
using PAIR = std::pair<ll, ll>;
using VS = std::vector<std::string>;
using VL = std::vector<long long>;
using VVL = std::vector<VL>;
using VVVL = std::vector<VVL>;
using VD = std::vector<double>;
template<class T>
using V = std::vector<T>;

/* using std */
using std::cout;
constexpr char endl = '\n';
using std::cin;
using std::pair;
using std::string;
using std::stack;
using std::queue;
using std::vector;
using std::list;
using std::map;
using std::unordered_map;
using std::multimap;
using std::unordered_multimap;
using std::set;
using std::unordered_set;
using std::unordered_multiset;
using std::multiset;
using std::bitset;
using std::priority_queue;

/* constant value */
constexpr ll MOD = 1000000007;
//constexpr ll MOD = 998244353;

/* Initial processing  */
struct Preprocessing { Preprocessing() { std::cin.tie(0); std::ios::sync_with_stdio(0); }; }_Preprocessing;

/* Remove the source of the bug */
inline signed pow(signed, signed) { assert(false); return -1; }

/* define hash */
namespace std {
template <>	class hash<std::pair<ll, ll>> { public:	size_t operator()(const std::pair<ll, ll>& x) const { return hash<ll>()(1000000000 * x.first + x.second); } };
}

/* input */
template<class T> std::istream& operator >> (std::istream& is, vector<T>& vec) { for (T& x : vec) is >> x; return is; }

//=============================================================================================

class PalindromicTree {
	class Node :public std::enable_shared_from_this<Node> {
		// 最大の回文接尾辞
		std::weak_ptr<Node> m_suffixLink;
		// 次サイズの回文(囲む文字, 次のNode)
		std::unordered_map<char, std::shared_ptr<Node>> m_edges;

		// 回文の右端itr
		std::list<int> m_itrs;
		// 回文サイズ
		const int m_size;

		// xAxとなるAを探す(x=str[itr])
		auto find(int itr, const std::string& s, bool flg = false) {
			// rootにたどり着いた
			if (m_size == -1) { return weak_from_this(); }
			// 現在地"A"において"xAx"となる
			if (itr - m_size - 1 >= 0 && s[itr] == s[itr - m_size - 1]) {
				return weak_from_this();
			}
			// 見つからない
			return m_suffixLink.lock()->find(itr, s, flg);
		}

		// 新しい回文Nodeを作成する
		auto create(int itr, const std::string& s) {
			// suffixLinkの探索
			auto suffixLinkFrom = m_suffixLink.lock()/*->m_suffixLink.lock()*/->find(itr, s, true).lock();
			// 新Nodeの作成
			auto newNode = std::make_shared<Node>(
				m_size + 2, (suffixLinkFrom->m_edges.find(s[itr]) == suffixLinkFrom->m_edges.end()) ?
				suffixLinkFrom->m_edges.find(' ')->second :
				suffixLinkFrom->m_edges.find(s[itr])->second);
			m_edges.emplace(s[itr], newNode);
			return std::weak_ptr<Node>(newNode);
		}

	public:
		// constructor
		Node(int size, const std::weak_ptr<Node>& suffixLink) :
			m_size(size),
			m_suffixLink(suffixLink) {}
		Node() :m_size(-1) {}


		// 次サイズの回文を追加
		auto add(int itr, const std::string& s) {
			auto addRoot = find(itr, s).lock();
			auto nextNode = (addRoot->m_edges.find(s[itr]) == addRoot->m_edges.end()) ?
				addRoot->create(itr, s) :
				std::weak_ptr<Node>(addRoot->m_edges.find(s[itr])->second);
			nextNode.lock()->m_itrs.emplace_back(itr);
			return nextNode;
		}

		// debug用
		auto outputTree(const std::string& s) ->void {
			if (m_size <= 0) { cout << "root"; } else {
				// 段
				for (int i = 0; (i < (m_size + 1) / 2); ++i) { cout << " |"; }
				cout << "- " << s.substr(*m_itrs.begin() - m_size + 1, m_size);
				// 右itr
				cout << " [ "; for (const auto& itr : m_itrs) { cout << itr << " "; }cout << "] ";
				// suffix link
				//auto p = m_suffixLink.lock();
				//cout << "{" << s.substr(*p->m_itrs.begin() - p->m_size + 1, p->m_size) << "} ";
			} cout << "\n";
			for (const auto& edge : m_edges) {
				if (m_size == -1 && edge.first == ' ') { continue; }
				edge.second->outputTree(s);
			}
		}

		// rootを決定
		auto isOddRoot(const std::weak_ptr<Node>& evenRoot) {
			m_suffixLink = weak_from_this();
			m_edges.emplace(' ', evenRoot);
		}
		/*
		 * lambda: (int size, list<int> rItr) -> void
		 */
		template<class Lambda>
		auto dfs_edges(const Lambda& lambda)->void {
			if (m_size > 0) { lambda(m_size, m_itrs); }
			for (const auto& edge : m_edges) {
				edge.second->dfs_edges(lambda);
			}
		}
	};

	// 対象となる文字列
	const std::string m_s;

	// 偶数長，奇数長のPalindromicTreeの根(0, -1)
	std::shared_ptr<Node> m_rootOdd;
	std::shared_ptr<Node> m_rootEven;
public:
	// constructor
	PalindromicTree(const std::string& s) :
		m_s(s),
		m_rootOdd(std::make_shared<Node>()),
		m_rootEven(std::make_shared<Node>(0, m_rootOdd)) {
		m_rootOdd->isOddRoot(m_rootEven);
		auto root = m_rootOdd;
		for (int r = 0; r < s.size(); ++r) {
			root = root->add(r, s).lock();
		}
	}

	/*
	 * lambda: (int size, list<int> rItr) -> void
	 */
	template<class Lambda>
	auto dfs_edges(const Lambda& lambda) {
		m_rootOdd->dfs_edges(lambda);
	}

	// debug用
	auto outputTree() {
		dump(m_s);
		cout << "-- even --\n";
		m_rootEven->outputTree(m_s);
		cout << "-- odd --\n";
		m_rootOdd->outputTree(m_s);
	}
};
signed main() {
	string s;
	cin >> s;
	auto p = PalindromicTree(s);
	ll ans = 0;
	p.dfs_edges([&](auto a, auto b) {if (a < s.size()) { chmax(ans, a); }});
	cout << ans << endl;
}