#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
const int inf = 1100;

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);	
	
	string s;
	cin>>s;

	int n=s.size();
	s=" "+s;

	vector dp(n+1,vector<i64>(2,inf));

	dp[1][0]=0;
	int m=(n+1)/2;
	if(n%2!=0){
		s.erase(m,1);
		m--;
		n--;
	}
	for(int i=1;i<=m;i++){
		if(s[i]==s[n-i+1]) dp[i+1][0]=min(dp[i+1][0],dp[i][0]);
		else{
			dp[i+1][1]=min(dp[i+1][1],dp[i][0]+1);
			if(i!=m) dp[i+2][0]=min(dp[i+2][0],dp[i][0]+2);
		}
		if(s[i]!=s[n-i+1]) dp[i+1][0]=min(dp[i+1][0],dp[i][1]);
		else{
			dp[i+1][1]=min(dp[i+1][1],dp[i][0]+1);
			if(i!=m) dp[i+2][0]=min(dp[i+2][0],dp[i][0]+2);
		}
	}
	i64 ans=min(dp[m+1][0],dp[m+1][1]);
	cout<<ans<<'\n';
	return 0;
}