#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/hash_policy.hpp>
#include <ext/pb_ds/hash_policy.hpp>
#define int long long
#define $AzH_TxdmN$ ios_base::sync_with_stdio(0);cin.tie(nullptr);cout.tie(nullptr);
#pragma GCC target("sse,sse2,sse3,ssse3,popcnt,abm,mmx,tune=native")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("no-stack-protector")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("fast-math")
#define ep emplace_back
#define pb push_back
#define pii pair<int,int>
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
using namespace std;
using namespace __gnu_pbds;
template <typename T>
using __indexed_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template <typename T>
using __indexed_multiset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
const int sz = 3e5+9;
const int LOG = 65;
const int MOD = 1e9+7;
const int INF = 1e18;
struct PT
{
struct Node
{
int next[26], link, len;
int occ;
};
string s;
vector<Node> t;
int siz, last, n;
int res;
PT(string& _s) : s(_s), n(_s.size()), res(0)
{
t.resize(n + 3);
t[0].len = -1;
t[1].len = 0;
t[0].link = t[1].link = 0;
siz = 2, last = 1;
for (int i = 0; i <= n; ++i)
{
for (int j = 0; j < 26; ++j)
{
t[i].next[j] = -1;
}
}
}
void extend(int i)
{
int cur = last, cur_len = 0, letter = s[i] - 'a';
while (true)
{
cur_len = t[cur].len;
if (i - cur_len - 1 >= 0 && s[i] == s[i - cur_len - 1])
{
break;
}
cur = t[cur].link;
}
if (t[cur].next[letter] != -1)
{
last = t[cur].next[letter];
t[last].occ++;
return;
}
last = siz++;
t[last].len = t[cur].len + 2;
t[last].occ = 1;
t[cur].next[letter] = last;
if (t[last].len == 1)
{
t[last].link = 1;
}
else
{
while (true)
{
cur = t[cur].link;
cur_len = t[cur].len;
if (i - cur_len - 1 >= 0 && s[i] == s[i - cur_len - 1])
{
t[last].link = t[cur].next[letter];
break;
}
}
}
}
void build()
{
for (int i = siz - 1; i >= 2; --i)
{
t[t[i].link].occ += t[i].occ;
}
}
void calllc()
{
for (int i = 2; i < siz; ++i)
{
res = max(res,t[i].len*t[i].occ);
}
}
};
string s;
void solve()
{
cin>>s;
PT pt(s);
for (int i = 0; i < (int)s.length(); ++i)
{
pt.extend(i);
}
pt.build();
pt.calllc();
cout<<pt.res<<'\n';
}
signed main()
{
$AzH_TxdmN$
int t = 1;
//cin >> t;
while (t--)
{
solve();
}
}
