#include <cstdio> 
#define Min(x, y) x < y ? x : y 
#define Max(x, y) x > y ? x : y 
using namespace std; 

int n = 0, p[22000009], ans; 
char s[22000009]; 

void get_S(); 

int main() {
	get_S(); 
	for (int i = 1, mid = 0, r = 0; i<= n; ++i) {
		p[i] = Min(p[(mid << 1) - r], r - i + 1); 
		while (s[i - p[i]] == s[i + p[i]]) ++p[i]; 
		if (i + p[i] - 1 > r) mid = i, r = p[i] + i - 1; 
		ans = Max(ans, p[i] - 1); 
	} 
	printf("%d\n", ans); 
	return 0; 
} 

void get_S() {
	s[++n] = '~'; s[++n] = '|'; 
	char c = getchar(); 
	while (c >= 'a' && c <= 'z') 
		s[++n] = c, s[++n] = '|', c = getchar(); 
}

rt， 在第15行本来应该是p[i] = Min(p[(mid << 1) - i], r - i + 1)， 但是错写成了p[i] = Min(p[(mid << 1) - r], r - i + 1)