#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}



struct RollingHash{
  using ull = unsigned long long;
  vector<ull> hash,p;
  RollingHash(){}
  RollingHash(const string &s,ull B=1000000007LL){
    int n=s.size();
    hash.assign(n+1,0);
    p.assign(n+1,1);
    for(int i=0;i<n;i++){
      hash[i+1]=hash[i]*B+s[i];
      p[i+1]=p[i]*B;
    }
  }
  //S[l, r)
  ull find(int l,int r){
    return hash[r]-hash[l]*p[r-l];
  }
};


vector<int> manacher(string s){
  int n=s.size();
  vector<int> v(n);
  for(int i=0,j=0;i<n;){
    while(i-j>=0&&i+j<n&&s[i-j]==s[i+j]) j++;
    v[i]=j;
    int k=1;
    while(i-k>=0&&i+k<n&&k+v[i-k]<j) v[i+k]=v[i-k],k++;
    i+=k;j-=k;
  }
  return v;
}

//INSERT ABOVE HERE
signed main(){
  string s;
  cin>>s;
  int n=s.size();
  string t(s);
  reverse(t.begin(),t.end());

  RollingHash rhs(s),rht(t);
  int ans=0;

  {
    string x;
    x.push_back('$');
    for(char c:s){
      x.push_back(c);
      x.push_back('$');
    }
    int ans1=0,ans2=0;
    auto v=manacher(x);
    for(int i=0;i<n*2+1;i++){
      if(i&1) chmax(ans1,v[i]-1);
      else chmax(ans2,v[i]-1);
    }
    if(ans1==n) ans1-=1;
    if(ans2==n) ans2-=2;
    chmax(ans,ans1);
    chmax(ans,ans2);
  }
  
  for(int i=1;i+1<n;i++){
    // erase i
    {
      int l=0,r=min(i+1,n-i);
      while(l+1<r){
        int m=(l+r)>>1;
        auto x=rhs.find(i+1,i+1+m);
        auto y=rht.find(n-i,n-i+m);
        if(x==y) l=m;
        else r=m;
      }
      chmax(ans,l*2);
    }
    // erase i, i+1
    if(i+2<n){
      int l=0,r=min(i+1,n-i-1);
      while(l+1<r){
        int m=(l+r)>>1;
        auto x=rhs.find(i+2,i+2+m);
        auto y=rht.find(n-i,n-i+m);
        if(x==y) l=m;
        else r=m;
      }
      chmax(ans,l*2+1);
    }
  }
  
  cout<<ans<<endl;
  return 0;
}