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

const int maxn = 1e5+3;
string s;
int n;
bool dp[maxn][4][4];
int ans;

int main() {
	ios_base::sync_with_stdio(0); cin.tie(0);
	cin >> s;
	n = s.size();

	memset(dp, false, sizeof dp);
	if (s[0] == s[n-1]) dp[1][0][0] = true;
	else dp[0][0][1] = dp[0][1][0] = true;
	for (int i=0; i<n/2; i++) {
		for (int hl=0; hl<4; hl++) {
			for (int hr=0; hr+hl<4; hr++) {
				int l = i + hl, r = n - 1 - i - hr;
				if (l >= r || !dp[i][hl][hr]) continue;
				if (s[l] == s[r]) dp[i+1][hl][hr] = true;
				else if (hl + hr + 1 < 4) dp[i][hl+1][hr] = dp[i][hl][hr+1] = true;
			}
		}
	}

	ans = 5;
	for (int hl=0; hl<4; hl++) {
		for (int hr=0; hr+hl<4; hr++) {
			int m = (n - hl - hr) / 2;
			if (dp[m][hl][hr]) ans = min(ans, hl+hr);
		}
	}

	cout << (ans == 5 ? -1 : ans) << '\n';
}