public class MergeList {
    private int head;
    private MergeList tail;

    public MergeList(int head, MergeList tail) {
	this.head = head;
	this.tail = tail;
    }

    private MergeList append(MergeList other) {
	if (tail == null) return new MergeList(head,other);
	else return new MergeList(head,tail.append(other));
    }

    private MergeList reverseAcc(MergeList acc) {
	if (tail == null) return new MergeList(head,acc);
	else return tail.reverseAcc(new MergeList(head,acc));
    }

    private MergeList reverse() {
	if (tail == null) return this;
	else return tail.reverse().append(new MergeList(head,null));
    }

    private MergeList merge(MergeList other) {
	if (other == null) return this;
	else if (head <= other.head)
	    if (tail != null) return new MergeList(head,tail.merge(other));
	    else return new MergeList(head,other);
	else return new MergeList(other.head,merge(other.tail));
    }
}