#include <bits/stdc++.h>
using namespace std;

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

int main(){
    int n, ans = 0;
    string s;
    cin >> s;
    n = s.size();
    string t = "$";
    for(int i = 0; i < s.size(); i++){
        t += s[i]; t += "$";
    }
    s = t;
    vector<int> len = manacher(s), left(s.size()), right(s.size());
    for(int i = 0; i < len.size(); i++){
        len[i]--;
        if(len[i] != n) ans = max(ans, len[i]);
        else ans = n - 1;
    }
    cout << ans << endl;
}