#include "bits/stdc++.h"
using namespace std;
#define ll long long
#define SZ(s) (ll)s.size()
int main() {
ios_base::sync_with_stdio(false); cin.tie(nullptr);
string s;
cin >> s;
int n = SZ(s);
ll ans = 1;
vector <pair <int, int>> vk;
vector <vector <pair <int, int>>> v, v1;
for(int c = 'a'; c <= 'z'; c++) {
v.clear();
v.resize(1);
for(int i = 0; i < n; i++) {
if(s[i] == char(c)) v[0].push_back({i, i});
}
v1.clear();
// cout << char (c) << '\n';
ll cnt = 1;
vector <int> vis(27);
while(SZ(v)) {
v1.clear();
// cout << cnt << '\n';
for(auto vv : v) {
// cout << SZ(vv) << ' ';
ans = max(ans, cnt * SZ(vv));
int nd = -1;
for(int i = 0; i < 26; i++) {
vis[i] = -1;
}
for(auto [l, r] : vv) {
if(l == 0 or r == n-1) continue;
if(s[--l] != s[++r]) continue;
if(vis[s[l]-'a'] == -1) {
vk = {{l, r}};
v1.push_back(vk);
vis[s[l]-'a'] = ++nd;
}
else {
v1[vis[s[l]-'a']].push_back({l, r});
}
}
}
v = v1;
cnt += 2;
// cout << '\n';
}
}
for(int c = 'a'; c <= 'z'; c++) {
v.clear();
v.resize(1);
for(int i = 0; i < n-1; i++) {
if(s[i] == char(c) and s[i+1] == char(c)) v[0].push_back({i, i+1});
}
// cout << char (c) << '\n';
v1.clear();
ll cnt = 2;
vector <int> vis(27);
while(SZ(v)) {
v1.clear();
// cout << cnt << '\n';
for(auto vv : v) {
// cout << SZ(vv) << ' ';
ans = max(ans, cnt * SZ(vv));
int nd = -1;
for(int i = 0; i < 26; i++) {
vis[i] = -1;
}
for(auto [l, r] : vv) {
if(l == 0 or r == n-1) continue;
if(s[--l] != s[++r]) continue;
if(vis[s[l]-'a'] == -1) {
vk = {{l, r}};
v1.push_back(vk);
vis[s[l]-'a'] = ++nd;
}
else {
v1[vis[s[l]-'a']].push_back({l, r});
}
}
}
v = v1;
cnt += 2;
// cout << '\n';
}
}
cout << ans;
return 0;
}
