#include<bits/stdc++.h>
using namespace std;
const int N = 4e7+10;
char a[N],b[N];
int p[N];
int len;
void init(){
    int k = 0;
    b[k++] = '$';
    b[k++] = '#';
    for(int i=0;i<len;i++){
        b[k++] = a[i];
        b[k++] = '#';
    }
    b[k++] = '^';
    len = k;
}
void manacher(){
    int mr = 1,mid;
    for(int i=0;i<len;i++){
        if(i < mr) p[i] = min(p[2*mid-i],mr-i);
        else p[i] = 1;
        while(b[i-p[i]] == b[i+p[i]]) p[i]++;
        if(i + p[i] > mr){
            mr = i + p[i];
            mid = i;
        }
    }
}
int main(){
    scanf("%s",a);
    len = strlen(a);
    init();
    manacher();
    int ans = 0;
    for(int i=0;i<len;i++) ans = max(ans,p[i]);
    cout<<ans - 1<<endl;
    return 0;
}