#include<stdio.h>
#include<string.h>
#define max(a,b) ((a>b) ? a:b)

int j,i,N,a[509][509];
char s[509],s2[509];

int main()
{
	freopen("palm.in","r",stdin);
	freopen("palm.out","w",stdout);
	
	gets(s+1);
	N=strlen(s+1);
	for (i=1;i<=N;i++)
		s2[i]=s[N-i+1];
	
	for (i=1;i<=N;i++)
		for (j=1;j<=N;j++)
			if (s[i]==s2[j]) a[i][j]=a[i-1][j-1]+1;
				else a[i][j]=max(a[i][j-1],a[i-1][j]);
	
	printf("%d\n",a[N][N]);
}