Description：

Solution：

Code：

#include<algorithm>

#include<iostream>

#include<cstdlib>

#include<cstdio>

#include<cmath>

#include<cctype>

#include<cstring>

using namespace std;

int n;

#define MAXN 300010

char c[MAXN];

struct node

{

    int tr[26];

    int fail,len;

}s[MAXN];

int ptr,last;

int cnt[MAXN];

int newnode(int l){s[ptr].len = l;return ptr++;}

void init()

{

    ptr = last = 0;

    newnode(0);

    newnode(-1);

    s[0].fail = 1;

    return;

}

int getfail(int i,int p)

{

    while(c[i - s[p].len - 1] != c[i])p = s[p].fail;

    return p;

}

void extend(int i,int k)

{

    int p = getfail(i,last);

    if(s[p].tr[k] == 0)

    {

        int np = newnode(s[p].len + 2);

        s[np].fail = s[getfail(i,s[p].fail)].tr[k];

        s[p].tr[k] = np;

    }

    last = s[p].tr[k];

    ++cnt[last];

    return;

}

int main()

{

    scanf("%s",c + 1);

    n = strlen(c + 1);

    init();

    for(int i = 1;i <= n;++i)extend(i,c[i] - 'a');

    for(int i = ptr;i >= 1;--i)cnt[s[i].fail] += cnt[i];

    long long ans = 0;

    for(int i = 1;i <= ptr;++i)ans = max(ans,1ll * cnt[i] * s[i].len);

    cout << ans << endl;

    return 0;

}