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)