#include <stdio.h>

int is_palindrome(char S[])
{
	int i, j;
	for (j = 0; S[j] != 0; j++);
	for (i = 0, j--; i < j; i++, j--) if (S[i] != S[j]) break;
	if (i < j) return 0;
	else return 1;
}

int is_unique(char S[])
{
	int i;
	for (i = 1; S[i] != 0; i++) if (S[i] != S[0]) break;
	if (S[i] != 0) return 0;
	else return 1;
}

int main()
{
	int l;
	char S[1000001];
	scanf("%s", S);
	for (l = 0; S[l] != 0; l++);
	if (is_palindrome(S) == 0) printf("%d\n", l);
	else if (is_unique(S) == 0) printf("%d\n", l - 2);
	else if (l % 2 == 0) printf("0\n");
	else printf("-1\n");
	fflush(stdout);
	return 0;
}