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

#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define FOR(i, a, b) for (int i = (a); i<(b); ++i)
#define RFOR(i, b, a) for (int i = (b)-1; i>=(a); --i)
#define MP make_pair
#define PB push_back
#define F first
#define S second
#define FILL(a, b) memset(a, b, sizeof(a))

typedef long long LL;
typedef pair<int, int> PII;
typedef vector<int> VI;

string s;

bool f(int l, int r, int k)
{
	if (k < 0) return false;
	if (l >= r) return true;
	
	if (s[l] == s[r]) return (f(l + 1, r - 1, k));
	return f(l + 1, r, k - 1) || f(l, r - 1, k - 1);
}

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	
	cin >> s;
	FOR (k, 0, 4)
	{
		if (f(0, SZ(s) - 1, k))
		{
			cout << k << '\n';
			return 0;
		}
	}
	cout << "-1\n";
		
	
	return 0;
}