#include <bits/stdc++.h>

using namespace std;
using ll = long long;

int main(){
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);

    //aabb->N
    //aaabaaa -> N-2
    //aaabbaaa -> N-2
    //aaa -> -1
    //aaaa ->0

    string S;
    cin >> S;
    int N = S.size();
    for (int i=0; i<N/2; i++){
        if (S[i] != S[N-1-i]){
            cout << N << endl;
            return 0;
        }
    }

    for (int i=0; i<N; i++){
        if (S[i] != S[0]){
            cout << N-2 << endl;
            return 0;
        }
    }

    cout << (N % 2 == 1 ? -1 : 0) << endl;

    return 0;
}