92，wa4，但是第四个样例是1.1e7个a，本地跑没问题，但是交上去就寄了呜呜呜，求助！！

#include <bits/stdc++.h>
using namespace std;
#define visit _visit
#define next _next
#define pb push_back
#define fi first
#define se second
#define endl '\n'
#define fast ios::sync_with_stdio(0), cin.tie(0)
#define int long long
#define ll long long
#define pint pair<int,int>

const int mod = 998244353;
const int maxn = 30000000;
const int INF = 0x3f3f3f3f;

void read(int &x){
	int f=1;x=0;char s=getchar();
	while(s<'0'||s>'9'){if(s=='-')f=-1;s=getchar();}
	while(s>='0'&&s<='9'){x=x*10+s-'0';s=getchar();}
	x*=f;
}
ll quick_pow(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll inv(ll x) {return quick_pow(x, mod-2);}
//----------------------------------------------------------------------------------------------------------------------//

int d[maxn];
vector<char>v;
void mlc(){
	d[0]=1;
	for(int i=1,l=0,r=0;i<v.size();i++){
		if(i<r){
			d[i]=min(d[l+r-i],r-i+1);
		}
		while(v[i-d[i]]==v[i+d[i]]){
			d[i]++;
		}
		if(i+d[i]-1>r){
			l=i-d[i]+1;
			r=i+d[i]-1;
		}
	}
} 
void solve(){
//	freopen("a.in", "r", stdin);
//	freopen("a.out", "w", stdout);
	string a;
	cin>>a;
	for(int i=0;i<a.size();i++){
		v.pb('#');
		v.pb(a[i]);
	}
	v.pb('#');
	mlc(); 
	int ans=0;
	for(int i=0;i<v.size();i++){
		if(v[i]=='#'){
			ans=max(ans,d[i]-1);
		}else{
			ans=max(ans,d[i]-1);
		}
	}
	cout<<ans<<endl;
}

signed main(){
	fast;
	int t=1;
	//cin>>t;
	while(t--){
		solve();
	}
	return 0;
}