#include <iostream>
#include <vector>

using namespace std;

int main() {
	string t; cin >> t;
	int n = t.length();
	vector<char> s(n+2);
	for (int i = 1; i <= n; i++) {
		s[i] = t[i-1];
	}
	vector<int> dp(n+2, 1e9);
	dp[0] = 0;
	for (int i = 1; i <= n/2 + 1; i++) {
		if (s[i] == s[n-i+1]) {
			dp[i] = min(dp[i], dp[i-1]);
		}
		if (i >= 2) {
			if ((s[i] != s[n-i+1] && s[i-1] != s[n-i+2]) || i == n/2 + 1) {
				dp[i] = min(dp[i], 1 + dp[i-2]);
			}
			else {
				dp[i] = min(dp[i], 2 + dp[i-2]);
			}
		}
	}
	/*
	for (int i = 0; i <= n; i++) {
		cout << dp[i] << ' ';
	}
	cout << endl;
	*/
	cout << dp[n/2 + 1] << endl;
}