def is_palindrome(s): return s == s[::-1] def all_same(s): return all(c == s[0] for c in s) 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)