#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();
int counter = 0;
map<pint, int> mapper;
vpint occsz;
vpint blocks; blocks.reserve(n);
for (int i = 0, lv = -1; i < n; i++) {
int c = s[i]-'a';
if (c != lv) blocks.push_back({c, 1});
else blocks[blocks.size()-1].second++;
lv = c;
}
sort(blocks.begin(), blocks.end());
int bs = blocks.size();
for (int i = 0; i < bs;) {
int j = i;
while (j < n && blocks[j].first == blocks[i].first) j++;
int ms = blocks[j-1].second;
vint cnt(ms);
for (int k = i; k < j; k++) cnt[blocks[k].second-1]++;
int mtv = 0; int tot = 0;
for (int k = ms-1; k >= 0; k--) {
mtv += (k+1)*cnt[k]; tot += cnt[k];
cnt[k] = mtv - k*tot;
}
pint pointer = {blocks[i].first, -1};
for (int k = 0; k < ms; k++) {
if (k > 0) pointer.second = mapper[pointer];
mapper[pointer] = counter++;
occsz.emplace_back(cnt[k], k+1);
}
i = j;
}
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};
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++; occsz.emplace_back(0, 0); }
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& [ct, sz]: occsz) res = max(res, ct*sz);
cout << res << endl;
return 0;
}
