template<typename IT,typename CMP>
void SM_sort(IT first,IT last,CMP cmp){ // 幫他寫了一個sort做測試
	if(last-first<=1)return;
	IT mid=kth(first,last,(last-first)/2,cmp);
	SM_sort(first,mid,cmp);
	SM_sort(mid+1,last,cmp);
}