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

#define rep(i, n) for(ll i = 0; i < n; i++)
#define rep2(i, m, n) for(ll i = m; i <= n; i++)
#define rrep(i, m, n) for(ll i = m; i >= n; i--)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define MAX(x) *max_element(all(x))
#define MIN(x) *min_element(all(x))
#define SZ(a) ((ll)(a).size())
using namespace std;
typedef long long ll;
typedef pair<int, int> P;
const ll mod = 1000000007;
const int dx[4] = { -1, 1, 0, 0 };
const int dy[4] = { 0, 0, 1, -1 };
const int inf = 1e9 + 1;
const ll INF = 1e18;
const double pi = acos(-1);

using Graph = vector<vector<ll>>;


//typedef atcoder::modint998244353 mint;
//typedef atcoder::modint1000000007 mint;


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


    string s; cin >> s;
    set<char> se;
    rep(i, SZ(s)) {
        se.insert(s[i]);
    }

    if (se.size() == 1) {
        if (SZ(s) == 1 or SZ(s) % 2 == 1) cout << -1 << endl;
        else cout << 0 << endl;
    }
    else {
        if (SZ(s) == 1) cout << -1 << endl;
        else {
            bool ok = false;
            rep(i, SZ(s) / 2) {
                if (s[i] != s[SZ(s) - 1 - i]) ok = true;
            }
            if (ok) cout << SZ(s) << endl;
            else cout << SZ(s) - 2 << endl;
        }
    }
}