定义一个Rectangle类，有长itsWidth、宽itsLength等属性，重载其构造函数Rectangle()和Rectangle(int width， int length)。

class Rectangle {
public:
Rectangle() {
itsWidth = 0;
itsLength = 0;
}
Rectangle(int width, int length) {
itsWidth = width;
itsLength = length;
}
private:
int itsWidth;
int itsLength;
};