如何实现这个C++点类呢？

class CMyPoint
{
friend istream& operator>>(istream& cin, CMyPoint& pt);
friend ostream& operator<<(ostream& cout, const CMyPoint& pt);
friend CMyPoint operator+(const CMyPoint& point1, const CMyPoint& point2);
friend CMyPoint operator-(const CMyPoint& point1, const CMyPoint& point2);
public:
CMyPoint() : m_x(0), m_y(0) {}
CMyPoint(int x, int y) : m_x(x), m_y(y){}
CMyPoint(const CMyPoint& point)
{
m_x = point.m_x;
m_y = point.m_y;
}
CMyPoint& operator=(const CMyPoint& point)
{
m_x = point.m_x;
m_y = point.m_y;
return *this;
}
CMyPoint& operator+=(const CMyPoint& point)
{
m_x += point.m_x;
m_y += point.m_y;
return *this;
}
CMyPoint& operator-=(const CMyPoint& point)
{
m_x -= point.m_x;
m_y -= point.m_y;
return *this;
}
private:
int m_x;
int m_y;
};

istream& operator>>(istream& cin, CMyPoint& pt)
{
cin>>pt.m_x;
cin>>pt.m_y;
return cin;
}

ostream& operator<<(ostream& cout, const CMyPoint& pt)
{
cout<<"("<<pt.m_x<<","<<pt.m_y<<")";
return cout;
}

CMyPoint operator+(const CMyPoint& point1, const CMyPoint& point2)
{
CMyPoint pt;
pt.m_x = point1.m_x + point2.m_x;
pt.m_y = point2.m_y + point2.m_y;
return pt;
}
CMyPoint operator-(const CMyPoint& point1, const CMyPoint& point2)
{
CMyPoint pt;
pt.m_x = point1.m_x - point2.m_y;
pt.m_y = point1.m_y - point2.m_y;
return pt;
}

int _tmain(int argc, _TCHAR* argv[])
{
CMyPoint pt1;
CMyPoint pt2;
CMyPoint pt3;
cin>>pt1>>pt2;
pt3 = pt1 + pt2;
cout<<pt3<<endl;
return 0;
}

输入: 2 2 3 3
输出：(5,6)