// Sea, You & Me
#include<bits/stdc++.h>
#define LL long long
#define DB double
#define MOD 998244353
#define ls(x) (x << 1)
#define rs(x) (x << 1 | 1)
#define lowbit(x) ((-x) & x)
#define MP make_pair
#define MT make_tuple
#define VI vector<int>
#define VL vector<LL>
#define VII VI::iterator
#define VLI VL::iterator
#define all(x) x.begin(), x.end()
#define EB emplace_back
#define PII pair<int, int>
#define SI set<int>
#define SII SI::iterator
#define fi first
#define se second
using namespace std;
template<typename T> void chkmn(T &a, const T b) { (a > b) && (a = b); }
template<typename T> void chkmx(T &a, const T b) { (a < b) && (a = b); }
void Inc(int &a, const int &b) { ((a += b) >= MOD) && (a -= MOD); }
void Dec(int &a, const int &b) { ((a -= b) < 0) && (a += MOD); }
void Mul(int &a, const int &b) { a = 1LL * a * b % MOD; }
void Sqr(int &a) { a = 1LL * a * a % MOD; }
int inc(const int &a, const int &b) { return (a + b >= MOD) ? a + b - MOD : a + b; }
int dec(const int &a, const int &b) { return (a - b < 0) ? a - b + MOD : a - b; }
int mul(const int &a, const int &b) { return 1LL * a * b % MOD; }
int sqr(const int &a) { return 1LL * a * a % MOD; }
int qwqmi(int x, int k = MOD - 2)
{
	int res = 1;
	while(k)
	{
		if(k & 1) Mul(res, x);
		k >>= 1, Sqr(x);
	}
	return res;
}
template<typename T> void read(T &x)
{
	x = 0;
	int f = 1;
	char ch = getchar();
	while(!isdigit(ch))
	{
		if(ch == '-')
			f = -1;
		ch = getchar();
	}
	while(isdigit(ch))
	{
		x = (x << 1) + (x << 3) + (ch ^ 48);
		ch = getchar();
	}
	x = x * f;
}
const int N = 1e6 + 5;
char ch[N];
int n;
int ans = 0;
struct PAM
{
	int idx, now;
	int len[N];
	int fail[N];
	int tr[N][26];
	void init()
	{
		idx = 1;
		len[1] = -1;
		fail[0] = fail[1] = 1;
	}
	int find(int x, int i)
	{
		while(ch[i] != ch[i - len[x] - 1])
			x = fail[x];
		return x;
	}
	void insert(int c, int i)
	{
		int x = find(now, i);
		if(!tr[x][c])
		{
			++idx;
			len[idx] = len[x] + 2;
			chkmx(ans, len[idx]);
			fail[idx] = tr[find(fail[x], i)][c];
			tr[x][c] = idx;
		}
		now = tr[x][c];
	}
}pam;
int main()
{
	scanf("%s", ch + 1);
	n = strlen(ch + 1);
	pam.init();
	for(int i = 1; i <= n; ++i)
		pam.insert(ch[i] - 'a', i);
	printf("%d\n", ans);
	return 0;
}