#include <bits/stdc++.h>

using namespace std;

inline int rd()
{
	int x=0;bool f=0;char ch=getchar();
	while(ch<'0' || ch>'9') {if(ch=='-') f=1;ch=getchar();}
	while(ch>='0' && ch<='9') x=(x<<3)+(x<<1)+(ch^48),ch=getchar();
	return f?-x:x;
}

#define x first
#define y second
#define vec vector
#define mp make_pair
#define pb emplace_back
#define upb upper_bound
#define lowb lower_bound
#define isz(x) (int)x.size()
#define gmx(a,b) (a=max(a,b))
#define gmn(a,b) (a=min(a,b))
#define fil(a,x) memset(a,x,sizeof(a))
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define per(i,a,b) for(int i=(a);i>=(b);i--)

/*

*/

typedef __int128 i128;
typedef long long LL;
typedef long double LD;
typedef unsigned long long ull;
typedef pair<int,int> PII;
typedef vector<int> VI;
typedef set<int>::iterator iter;
const int N=1e6+10;

int n,m;
char a[N],b[N<<1];

int d[N<<1];
void manacher() {
	b[++m]='@'; rep(i,1,n) b[++m]='#',b[++m]=a[i];
	b[++m]='#',b[++m]='$',d[1]=1;
	for(int i=2,md=1,mr=1;i<=m;i++) {
		if(i<=mr) d[i]=min(d[md-(i-md)],mr-i+1);
		else d[i]=1,md=mr=i;
		while(i+d[i]<=m && b[i-d[i]]==b[i+d[i]]) ++d[i];
		if(i+d[i]-1>=mr) mr=i+d[i]-1,md=i;
	}
	// rep(i,1,m) cerr<<d[i]<<' '; cerr<<"\n";
	// cerr<<(b+1)<<"\n";
}

signed main()
{
	scanf("%s",a+1),n=strlen(a+1);
	manacher(); int ans=0;
	rep(i,1,m) gmx(ans,d[i]-1);
	printf("%d\n",ans);

	return 0;
}