//https://ncode.syosetu.com/n4830bu/001/
#include <bits/stdc++.h>
using namespace std;

struct PalindromicTree {
    PalindromicTree() {
        node* size_m1 = create_node();
        size_m1->suffix_link = 0;
        size_m1->len = -1;
        node* size_0 = create_node();
        size_0->suffix_link = 0;
        size_0->len = 0;
        active_idx = 0;
    }
    struct node {
        map<char, int> link;
        int suffix_link, len, count;
    };
    vector<node> nodes;
    string S;
    int active_idx;
    node* create_node() {
        nodes.emplace_back();
        node* ret = &nodes.back();
        ret->count = 0;
        return ret;
    }
    int find_prev_palindromic_idx(int node_id) {
        const int pos = (int)S.size() - 1;
        while (true) {
            const int opposite_side_idx = pos - 1 - nodes[node_id].len;
            if (opposite_side_idx >= 0 && S[opposite_side_idx] == S.back()) break;
            node_id = nodes[node_id].suffix_link;
        }
        return node_id;
    }
    void add(char ch) {
        S += ch;
        const int prev = find_prev_palindromic_idx(active_idx);
        const auto inserted_result = nodes[prev].link.insert(make_pair(ch, (int)nodes.size()));
        active_idx = inserted_result.first->second;
        if (!inserted_result.second) {
            nodes[active_idx].count++;
            return;
        }
        node* new_node = create_node();
        new_node->count = 1;
        new_node->len = nodes[prev].len + 2;
        if (new_node->len == 1) {
            new_node->suffix_link = 1;
        } else {
            new_node->suffix_link = nodes[find_prev_palindromic_idx(nodes[prev].suffix_link)].link[ch];
        }
    }
    vector<int> build_frequency() {
        vector<int> frequency(nodes.size());
        for (int i = (int)nodes.size() - 1; i > 0; i--) {
            frequency[i] += nodes[i].count;
            frequency[nodes[i].suffix_link] += frequency[i];
        }
        return frequency;
    }
};

int main() {
    string S;
    cin >> S;
    PalindromicTree eertree;
    for (auto&& c : S) {
        eertree.add(c);
    }
    int ans = 0;
    for (auto&& node : eertree.nodes) {
        if (node.len != S.size())
            ans = max(ans, node.len);
    }
    cout << ans << endl;
}