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

int main() {
	string s;
	cin >> s;
	int n = s.size();
	int k = count(s.begin(), s.end(), s[0]);
	if(n == k)
		puts(n & 1 ? "-1" : "0");
	else {
		if(s == string{s.rbegin(), s.rend()})
			cout << n - 2 << endl;
		else
			cout << n << endl;
	}
}