english: There are no further restrictions and we thus get a subset of {1,2,3…,n−2} \{1, 2, 3 \ldots , n - 2 \} {1,2,3…,n−2} that satisfies the conditions and we union it with {n} \{ n \} {n}.
non_english: うぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅうぐぅぅうぐぅうぐぅぐ～ぐ～ぐ～。。。。