#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 310000;
const int K = 26;
int s[N], len[N], lnk[N], to[N][K], cnt[N], n, suff, last;
void init() {
s[n++] = -1;
lnk[0] = 1;
len[1] = -1;
last = 1;
}
int get_link(int v) {
while (s[n - len[v] - 2] != s[n - 1])
v = lnk[v];
return v;
}
void add_char(int c) {
s[n++] = c;
suff = get_link(suff);
if (!to[suff][c]) {
last++;
len[last] = len[suff] + 2;
lnk[last] = to[get_link(lnk[suff])][c];
to[suff][c] = last;
}
suff = to[suff][c];
cnt[suff]++;
}
void count() {
for (int i = last; i >= 0; i--)
cnt[lnk[i]] += cnt[i];
}
int solve() {
int ans = 0;
for (int i = 0; i <= last; i++)
ans = max(ans, len[i] * cnt[i]);
return ans;
}
int32_t main() {
ios::sync_with_stdio(0); cin.tie(0);
init();
string s; cin >> s;
for (char c : s)
add_char(c - 'a');
count();
cout << solve();
}
