#include <iostream>
#include <string>
#include <set>

using namespace std;

int main(){
    string s;
    cin >> s;
    int n = s.size();

    set<int> u;

    for (int i = 0; i < n; i++){
        if (s[i] != s[n - i - 1]){
            cout << n << endl;
            return 0;
        }
        u.insert(s[i]);
    }

    if (int(u.size()) == 1){
        cout << (n & 1? -1: 0) << endl;
    }
    else{
        cout << (n == 3? -1: n - 2) << endl;
    }
}