void Test15()
{
	int k = 3;
	List l;
	for(int i = 1; i<=10; ++i)
	{
		l.PushBack(i);
	}
	l.Print();
	cout << "3:" << l.Back_K(k)->_data << endl;
	k = 10;
	cout << "10:" << l.Back_K(k)->_data << endl;
	k = 1;
	cout << "1:" << l.Back_K(k)->_data << endl;
}