#include<stdio.h>
int main()
{
	char s[1000006];
	scanf("%s", s);
	int i, n = 0;
	while (s[n] != '\0')
		n++;
	int cnt = 0;
	for (i = 0; i < n / 2; i++)
		if (s[i] != s[n - i - 1])
			cnt++;
	if (cnt > 0)
	{
		printf("%d\n", n);
		return 0;
	}
	for (i = 0; i < n / 2; i++)
		if (s[i] != s[0])
			cnt++;
	if (cnt > 0)
	{

		printf("%d\n", n - 2);
		return 0;
	}
	if (n % 2 == 0)
		printf("0\n");
	else if (s[0] != s[(n - 1) / 2] && n >= 5)
		printf("%d\n", n - 2);
	else
		printf("-1\n");
	return 0;
}