#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

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

const int N = 107;

void updMin(int& x, int val) {
	x = min(x, val);
}

int dp[N][2][2];

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	string s;
	cin >> s;
	int n = SZ(s);
	RFOR(i, n / 2, 0) {
		int l = i, r = n - 1 - i;
		FOR(cl, 0, 2) FOR(cr, 0, 2) {
			dp[i][cl][cr] = N;
			FOR(dl, 0, 2) FOR(dr, 0, 2) {
				if ((s[l] == s[r] && ((cl || dl) == (cr || dr))) || (s[l] != s[r] && (cl || dl || cr || dr))) {
					if (n % 2 == 0 && i == n / 2 - 1) {
						if (dl == dr) {
							updMin(dp[i][cl][cr], dl);
						}
					}
					else {
						updMin(dp[i][cl][cr], dp[i + 1][dl][dr] + dl + dr);
					}
				}
			}
		}
	}
	cout << dp[0][0][0] << "\n";
	return 0;
}