def is_palindrome(s):
    left = 0
    right = len(s) - 1
    while left < right:
        if s[left] != s[right]:
            return False
        left += 1
        right -= 1
    return True

def all_same(s):
    if not s:
        return True
    first = s[0]
    for c in s:
        if c != first:
            return False
    return True

s = input().strip()
if not is_palindrome(s):
    print(len(s))
else:
    if all_same(s):
        if len(s) % 2 == 0:
            print(0)
        else:
            print(-1)
    else:
        print(len(s) - 2)