#include <bits/stdc++.h>
using namespace std;
using i64 = int64_t;
using vi = vector<i64>;
using vvi = vector<vi>;

vi manacher(string s) {
    int n = s.size();
    vi ret(n);
    for (int i = 0, j = 0; i < n;) {
        while (i - j >= 0 && i + j < n && s[i - j] == s[i + j]) j++;
        ret[i] = j;
        int k = 1;
        while (i - k >= 0 && i + k < n && k + ret[i - k] < j) {
            ret[i + k] = ret[i - k];
            k++;
        }
        i += k;
        j -= k;
    }
    return ret;
}

int main() {
    string s;
    cin >> s;
    string t = "$";
    for (char c: s) {
        t += c;
        t += '$';
    }
    vi m = manacher(t);
    int maxlen = *max_element(m.begin(), m.end()) - 1;
    if (maxlen == s.size()) {
        cout << maxlen - 1 << endl;
    } else {
        cout << maxlen << endl;
    }
}