#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
int main() {
	set<char> st;
	string s;
	cin >> s;
	int n = s.size();
	for (int i = 0; i < n; i++) {
		if (s[i] != s[n - i - 1]) {
			cout << n << endl;
			return 0;
		}
		st.insert(s[i]);
	}
	if (st.size() == 1) {
		if (n % 2 == 1) {
			cout << -1 << endl;
		}
		else {
			cout << 0 << endl;
		}
	}
	else {
		if (n == 3) {
			cout << -1 << endl;
		}
		else {
			cout << n - 2 << endl;
		}
	}
}