#include <iostream>
using namespace std;

char s[] ="abcaaabca";
int size(char s[])
{int i; i=-1; while (s[++i]!='\0');return --i;}
int min(int i, int j){if (i<j) return i; else return j;}
int tsz(int i, int j) {
	if (i>=j) return 0 ;
	if (s[i]==s[j]) return tsz(i+1,j-1); 
	return min(tsz(i+1,j),tsz(i,j-1))+1 ;	
}
int main(){
printf("%d",tsz(0,size(s)));
}