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

int main() {
    string S;
    cin >> S;
    string T = S;
    reverse(T.begin(),T.end());
    string R = S;
    sort(R.begin(),R.end());
    if(S == T) {
        if(S.size() == 3 || (S.size()%2 && R.front() == R.back())) {
            cout << -1 << endl;
        }
        else if(R.front() == R.back()) {
            cout << 0 << endl;
        }
        else {
            cout << S.size()-2 << endl;
        }
    }
    else {
        cout << S.size() << endl;
    }
}