#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
ll sqr(const ll&x){
	return x*x;
}
void maxify(ll&x,const ll&y){
	y>x&&(x=y);
}
const int max_n=1000000;
struct node{
	int len,fail,cnt,sn[26];
};
char str[max_n+2];
struct pam_t{
	node tr[max_n+1];
	int now,nodcnt;
	void clearsn(const int u){
		memset(tr[u].sn,0,sizeof(tr[u].sn));
	}
	void init(){
		nodcnt=1;
		tr[0].len=0,tr[0].fail=1;
		clearsn(1);
		tr[1].len=-1,tr[1].fail=0;
		clearsn(2);
		now=1;
	}
	void append(const int i){
		const int ch=str[i];
		while(str[i-tr[now].len-1]!=ch)
			// fprintf(stderr,"*%d\n",now),
			now=tr[now].fail;
		// fprintf(stderr,"par %d\n",now);
		if(!tr[now].sn[ch]){
			const int v=++nodcnt;
			tr[v].len=tr[now].len+2;
			// fprintf(stderr,"%d\n",tr[v].len);
			tr[v].cnt=0,clearsn(v);
			int j=tr[now].fail;
			// fprintf(stderr,"%d %d\n",j,i-tr[j].len-1);
			for(; str[i-tr[j].len-1]!=ch; j=tr[j].fail);
			// fprintf(stderr,"&& %d %d\n",j,ch);
			tr[v].fail=tr[j].sn[ch];
			tr[now].sn[ch]=v;
		}
		++tr[now=tr[now].sn[ch]].cnt;
		// fprintf(stderr,"%d: %d  %d\n",i,now,tr[now].fail);
	}
	void solve(){
		ll ans=0;
		for(int i=nodcnt; i>1; --i){
			// fprintf(stderr,"%d: %d %d\n",i,tr[i].len,tr[i].cnt);
			tr[tr[i].fail].cnt+=tr[i].cnt;
			maxify(ans,sqr(tr[i].len)*tr[i].cnt);
		}
		printf("%lld\n",ans);
	}
}pam;
int main(){
	scanf("%s",str+1);
	str[0]=26;
	const int n=strlen(str+1);
	pam.init();
	for(int i=1; i<=n; ++i){
		str[i]-='a';
		pam.append(i);
	}
	pam.solve();
	return 0;
}