#line 1 "Main.cpp"
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <atcoder/modint>
#line 1 "nachia\\string\\enumerate-palindromes.hpp"

#line 4 "nachia\\string\\enumerate-palindromes.hpp"


namespace nachia{

std::vector<int> EnumeratePalindromes(const std::string& S) {
    int n = S.size();
    if (n == 0) return { 0 };
    std::string sx(n * 2 + 1, '$');
    for (int i = 0; i < n; i++) sx[i * 2 + 1] = S[i];
    n = n * 2 + 1;
    std::vector<int> res(n);
    int r = 0;
    for (int i = 0; i < n; ) {
        while ((0 <= i - r && i + r < n) ? (sx[i - r] == sx[i + r]) : false) r++;
        res[i] = r;
        int di = 1;
        while ((0 <= i - di && i + di < n) ? (res[i - di] < r - di) : false) {
            res[i + di] = res[i - di];
            di++;
        }
        r -= di;
        i += di;
    }
    for (int i = 0; i + 1 < n; i++) res[i] = res[i + 1] - 1;
    res.resize(n - 2);
    return res;
}

} // namespace nachia
#line 7 "Main.cpp"
using namespace std;
using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
#define rep(i,n) for(int i=0; i<(int)(n); i++)
const i64 INF = 1001001001001001001;

using Modint = atcoder::static_modint<998244353>;

int main(){
    string S; cin >> S;
    auto P = nachia::EnumeratePalindromes(S);
    int N = S.size();
    vector<int> dp(N+1, -1);
    dp[0] = 1000000;
    rep(i,P.size()){
        for(int c=1-i%2; c<=P[i]; c+=2){
            int s = (i-c+1)/2;
            dp[s+c] = max(dp[s+c], min(dp[s], c));
        }
    }
    cout << dp[N] << endl;
    return 0;
}



struct ios_do_not_sync{
    ios_do_not_sync(){
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
    }
} ios_do_not_sync_instance;