#include<bits/stdc++.h>
using lint=long long;
int main(){
    std::cin.tie(nullptr);std::ios_base::sync_with_stdio(false);
    std::cout.setf(std::ios_base::fixed);std::cout.precision(15);
    std::string s;std::cin>>s;
    {
        std::string swp="$";
        for(char c:s){
            swp.push_back(c);
            swp.push_back('$');
        }
        swp.swap(s);
    }
    lint n=s.length();
    std::vector<lint>a(n);
    for(lint i=0,j=0;i<n;){
        for(;0<=i-j&&i+j<n&&s.at(i-j)==s.at(i+j);j++);
        a.at(i)=j;
        lint k=1;
        for(;0<=i-k&&k+a.at(i-k)<j;k++){
            a.at(i+k)=a.at(i-k);
        }
        i+=k,j-=k;
    }
    lint ans=0;
    for(lint i=0;i<n;i++){
        lint x=a.at(i)-1;
        if(x<n&&ans<x)ans=x;
    }
    std::cout<<ans<<'\n';
}