#include <iostream>
#include <cstring>
#include <algorithm>

const int N = 2e7 + 10;

char a[N], b[N];
int p[N];

int len, n;
void init()
{
    b[len ++] = '$', b[len ++] = '#';

    for(int i = 0; i < n; i ++)
    {
        b[len ++] = a[i];
        b[len ++] = '#';
    }
    b[len ++] = '^';
    n = len;
    return;
}

void manacher() // 求最长回文串
{
    int mr = 0, mid = 0;
    for(int i = 0; i < n; i ++)
    {
        if(i < mr) p[i] = std :: min(p[2 * mid - i], mr - i);
        else p[i] = 1;

        while(b[i - p[i]] == b[i + p[i]]) p[i] ++;

        if(i + p[i] > mr)
        {
            mr = i + p[i];
            mid = i;
        }
    }
}
int main()
{
    std :: cin >> a;
    n = strlen(a);
    init();
    manacher();

    int res = 0;
    for(int i = 0; i < n; i ++) res = std :: max(res, p[i]);
    std :: cout << res - 1 << "\n";
    return 0;
}