#include<cstring>

 #include<cstdio>

 #include<algorithm>

 #define N (22000010)

 using namespace std;

 int n, ans, mid, mx;

 int p[N];

 char tmp[N],s[N];

 inline int max(int a, int b){return a>b?a:b;}

 int main(){

     scanf("%s", tmp+); n=strlen(tmp+);

     for(int i=;i<=n;i++) s[i<<]=tmp[i], s[i<<|]='#';

     n=(n<<)+;

     s[]=s[n]='#';

     ans=mid=mx=;

     for(int i=;i<=n;i++){

         if(mx>i) p[i]=min(p[(mid<<)-i],mx-i);

             else p[i]=;

         while(s[i-p[i]]==s[i+p[i]]) p[i]++;

         if(p[i]+i>mx) mx=p[i]+i, mid=i;

         ans=max(ans, p[i]);

     }

     return printf("%d\n", ans-),;

 }