#include "bits/stdc++.h"
//#include "atcoder/all"
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
//const bool debug = false;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	string s; cin >> s;
	if (1 == s.size()) {
		cout << -1 << endl;
		return 0;
	}
	{
		bool b = true;
		rep(i, s.size()) {
			if (s[i] != s[s.size() - 1 - i])b = false;
		}
		if (!b) {
			cout << s.size() << endl;
			return 0;
		}
	}
	{
		bool b = true;
		rep(i, s.size()) if (s[0] != s[i])b = false;
		if (b || (3 >= s.size())) {
			cout << 0 << endl;
			return 0;
		}
		else {
			cout << s.size() - 2 << endl;
		}
	}
	return 0;
}