#include "bits/stdc++.h"
#define int long long

using namespace std;
using ll = long long;
using P = pair<ll, ll>;
const ll INF = (1LL << 61);
ll mod = 1000000007;

signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	string S; cin >> S;
	int N = S.size();
	if (N == 1) {
		cout << -1 << endl; return 0;
	}
	string T = S;
	reverse(T.begin(), T.end());
	if (S != T) {
		cout << N << endl; return 0;
	}
	
	char c = S[0];
	bool ok = true;
	for (int i = 0; i < N; i++)if (c != S[i])ok = false;
	if (ok) {
		if (N % 2 == 1)cout << -1 << endl;
		else cout << 0 << endl;
	}
	else {
		if (N == 3)N = 1;
		cout << N - 2 << endl; 
	}
	return 0;


}