#include <bits/stdc++.h>
using namespace std;
using vint = vector<int>;
using ll = long long;
using vll = vector<ll>;
using pint = pair<int, int>;
using vpint = vector<pint>;
using pll = pair<ll, ll>;
using vpll = vector<pll>;
using pill = pair<int, ll>;
using vpill = vector<pill>;
using plli = pair<ll, int>;
using vplli = vector<plli>;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
string s; cin >> s;
int n = s.size();
vint count(26);
for (char c: s) count[c - 'a']++;
int counter = 0;
map<pint, int> mapper;
for (int i = 0; i < 26; i++) mapper[{i, -1}] = counter++;
map<int, pint> occsz;
for (int i = 0; i < 26; i++) occsz[mapper[{i, -1}]] = {count[i], 1};
set<pint> pstart;
pstart.insert({0, mapper[{s[0]-'a', -1}]});
for (int i = 1; i < n; i++) {
int c = s[i] - 'a';
int lv = s[i-1] - 'a';
pint insval;
if (c != lv) insval = {i, mapper[{c, -1}]};
else {
auto it = pstart.end()--;
pint nv = {c, it->second};
if (!mapper.count(nv)) mapper[nv] = counter++;
insval = {it->first, mapper[nv]};
}
for (auto it = pstart.begin(); it != pstart.end(); it = pstart.erase(it)) {
if (it->first == 0) continue;
int lst = s[it->first-1] - 'a';
if (lst == c) {
pint nv = {c, it->second};
if (!mapper.count(nv)) mapper[nv] = counter++;
int mnv = mapper[nv], mst = it->second;
occsz[mnv] = {occsz[mnv].first+1, occsz[mst].second+2};
pint nstart = {it->first-1, mnv};
if (nstart.first != 0) pstart.insert(nstart);
}
}
pstart.insert(insval);
}
int res = 0;
for (auto& [key, val]: occsz) res = max(res, val.first*val.second);
cout << res << endl;
return 0;
}
