#include <bits/stdc++.h>
using namespace std;
const int maxn = 1.1e7 + 5;
char s[maxn], a[maxn*2+1];
int n, p[maxn*2+1], mid, mr, ans;

int main() {
	scanf("%s", s);
	a[n++] = '$';
	a[n++] = '#';
	for (int i = 0; s[i]; i++)
		a[n++] = s[i], a[n++] = '#';
	a[n++] = '^';
	for (int i = 0; i < n; i++) {
		if (i < mr) 
			p[i] = min(p[2 * mid - i], mr - i);
		else 
			p[i] = 1;
		while (a[i-p[i]] == a[i+p[i]]) 
			p[i]++;
		if (i + p[i] > mr) {
			mr = i + p[i];
			mid = i;
		}
		ans = max(ans, p[i] - 1);
	}
	printf("%d\n", ans);
	return 0;
}