def is_palindrome(s):
    return s == s[::-1]

def main():
    s = input().strip()
    n = len(s)
    if not is_palindrome(s):
        print(n)
        return

    all_same = True
    first_char = s[0]
    for c in s:
        if c != first_char:
            all_same = False
            break

    if all_same:
        if n % 2 == 0:
            print(0)
        else:
            print(-1)
        return

    # Else, not all characters are the same and it's a palindrome
    candidate = n - 2
    print(candidate if candidate >= 0 else -1)

if __name__ == "__main__":
    main()