1、按下列要求编程：

class Recangle{
private:
int width;
int length;
public:
Recangle()
{width = 0; length = 0;};
Recangle(int w,int h)
{width = w; height = h;};
int circumference()
{return 2*(width+height)};
int Area()
{return width * height};
void changeRec(int w,int h)
{width = w; height = h;};
};