#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, srt, end) for (long long i = (srt); i < (long long)(end); i++)

void solve() {
    string s;
    cin >> s;
    string t(s.rbegin(), s.rend());
    if(t != s) {
        cout << s.size() << endl;
    } else {
        if(s == string(s.size(), s.front())) {
            cout << (s.size() % 2 ? -1 : 0) << endl;
        } else {
            cout << s.size() - 2  << endl;
        }
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    solve();
    return 0;
}