#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int maxn=100010;
struct trees{int len,fail,t[260];}t[maxn];
char s[maxn];
int n,len,l,sz,ans;
int getfail(int x)
{
    while(s[len-t[x].len-1]!=s[len])x=t[x].fail;
    return x;
}
void tree_work()
{
    int x=s[++len];
    l=getfail(l);
    if(!t[l].t[x])
    {
        sz++;
        t[sz].len=t[l].len+2;
        if(t[sz].len>ans)ans=t[sz].len;
        t[sz].fail=t[getfail(t[l].fail)].t[x];//偏小 
        t[l].t[x]=sz;
    }
    l=t[l].t[x];
}
int main()
{
    scanf("%s",s+1);
    n=strlen(s+1);
    sz=1;
    s[0]=-1;//
    t[0].len=0;t[1].len=-1;
    t[0].fail=t[1].fail=1;
    len=l=ans=0;
    for(int i=1;i<=n;i++)tree_work();
    printf("%d",ans);
    return 0;
}