def is_palindrome(s):
    n = len(s)
    for i in range(n // 2):
        if s[i] != s[n - 1 - i]:
            return False
    return True

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

s = input().strip()
n = len(s)

if not is_palindrome(s):
    print(n)
else:
    if all_same(s):
        if n % 2 == 0:
            print(0)
        else:
            print(-1)
    else:
        print(n - 2)