#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <queue>
#include <ctime>
#include <cassert>
#include <complex>
#include <string>
#include <cstring>
#include <chrono>
#include <random>
#include <bitset>
#include <fstream>
using namespace std;
#define int long long
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
#define bp __builtin_popcountll
#define ll long long
#define mp make_pair
#define x first
#define y second
#define Time (double)clock()/CLOCKS_PER_SEC
#define debug(x) std::cerr << #x << ": " << x << '\n';
#define FOR(i, n) for (int i = 0; i < n; ++i)
#define FORN(i, n) for (int i = 1; i <= n; ++i)
#define pb push_back
#define trav(a, x) for (auto& a : x)
using vi = vector<int>;
template <typename T>
std::istream& operator >>(std::istream& input, std::vector<T>& data)
{
for (T& x : data)
input >> x;
return input;
}
template <typename T>
std::ostream& operator <<(std::ostream& output, const pair <T, T> & data)
{
output << "(" << data.x << "," << data.y << ")";
return output;
}
template <typename T>
std::ostream& operator <<(std::ostream& output, const std::vector<T>& data)
{
for (const T& x : data)
output << x << " ";
return output;
}
ll div_up(ll a, ll b) { return a/b+((a^b)>0&&a%b); } // divide a by b rounded up
ll div_down(ll a, ll b) { return a/b-((a^b)<0&&a%b); } // divide a by b rounded down
ll math_mod(ll a, ll b) { return a - b * div_down(a, b); }
#define tcT template<class T
#define tcTU tcT, class U
tcT> using V = vector<T>;
tcT> void re(V<T>& x) {
trav(a, x)
cin >> a;
}
tcT> bool ckmin(T& a, const T& b) {
return b < a ? a = b, 1 : 0;
} // set a = min(a,b)
tcT> bool ckmax(T& a, const T& b) {
return a < b ? a = b, 1 : 0;
}
ll gcd(ll a, ll b) {
while (b) {
tie(a, b) = mp(b, a % b);
}
return a;
}
const int N = 3e5 + 7, C = 26;
int to[N][C], link[N], len[N];
int term[N];
signed main() {
#ifdef LOCAL
#else
#define endl '\n'
ios_base::sync_with_stdio(0); cin.tie(0);
#endif
string s;
cin >> s;
int n = s.size();
//0 - odd root
//1 - even root
auto up = [&](int u, int r, char c) {
while (u && (r - len[u] < 0 || s[r - len[u]] != c))
u = link[u];
return u;
};
len[0] = -1;
int ptr = 2;
int u = 1;
for (int i = 0; i < n; ++i) {
int c = s[i] - 'a';
u = up(u, i - 1, s[i]);
if (!to[u][c]) {
len[ptr] = len[u] + 2;
int v = up(link[u], i - 1, s[i]);
if (to[v][c])
v = to[v][c];
else
v = 1;
link[ptr] = v;
to[u][c] = ptr;
++ptr;
}
u = to[u][c];
term[u]++;
}
for (int i = ptr - 1; i >= 0; --i) {
term[link[i]] += term[i];
}
int ans = 0;
FOR (i, ptr) {
ckmax(ans, len[i] * term[i]);
}
cout << ans << endl;
}
