#include <iostream>
#include <string>
#include <algorithm>
#include <functional>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <tuple>
#include <cstdio>
#include <cmath>
#include <bitset>
//#include <atcoder/all>


#define ll long long
#define rep(i, n) for(ll i = 0; i < n; i++)
using namespace std;
//using namespace atcoder;

const ll INF = 1e18;

/*
ll gcd(ll a, ll b){
	//log max(a,b)
	if (a % b == 0){
		return(b);
	}
	else{
		return(gcd(b, a % b));
	}
}

ll lcm(ll a, ll b){
	return a * b / gcd(a, b);
}
*/
//gcd lcm
/*
class UnionFind {
public:
	vector<ll> par;

	void init(ll sz) {
		par.resize(sz, -1);
	}
	ll root(ll pos) {
		if (par[pos] == -1) return pos;
		par[pos] = root(par[pos]);
		return par[pos];
	}
	void unite(ll u, ll v) {
		u = root(u); v = root(v);
		if (u == v) return;
		par[u] = v;
	}
	bool same(ll u, ll v) {
		if (root(u) == root(v)) return true;
		return false;
	}
};
*/
typedef pair<ll, ll> P;

int main() {
	map<char, int> mp;
	string s;
	cin >> s;
	bool p = true;
	if (s.size() == 1) {
		cout << -1 << endl;
		return 0;
	}
	rep(i, (ll)s.size()) {
		mp[s[i]]++;
	}
	if (mp.size() == 1) {
		if (s.size() % 2) cout << 1 << endl;
		else cout << 0 << endl;
		return 0;
	}
	for (ll i = 0; i < (ll)s.size() / 2; i++) {
		if (s[i] != s[s.size() - i - 1]) p = false;
	}
	if (!p) cout << s.size() << endl;
	else {
		cout << s.size() - 2 << endl;
	}
	return 0;
}