#include<iostream>
#include<cstdio>
using namespace std;
char s[22000010],ch;
int c,r,p[22000010],n=1,ans;
int main(){
	s[0]='~',s[1]='|';
	while(scanf(" %c",&ch)!=EOF)s[++n]=ch,s[++n]='|';
	for(int i=1;i<=n;i++){
		if(i<r)p[i]=min(r-i+1,p[(c<<1)-i]);
		while(s[i-p[i]]==s[i+p[i]])p[i]++;
		if(i+p[i]-1>=r)r=i+p[i]-1,c=i;
		ans=max(ans,p[i]);
	}
	printf("%d",ans-1);
}
//对应洛谷 P3805 【模板】manacher