设计一个Point类，包含一个构造函数及计算两点间距离的成员函数(数据成员自行确定)。

#include <iostream>
using namespace std;
#include <cstdlib>
#include <cmath>
class Point
{
private:
int x,y;
public:
Point (int xx,int yy)
{
x=xx;y=yy;
}
friend long Sfc (Point a,Point b);
};
long Sfc (Point a,Point b)
{
long c=abs(a.y-b.y),k=abs(a.x-b.x);
return c*k;
}
int main (void)
{
int x1,y1,x2,y2;
cout<<"Enter p1 x y:";cin>>x1>>y1;
cout<<"Enter p2 x y:";cin>>x2>>y2;
Point p1(x1,y1),p2(x2,y2);
cout<<"S="<<Sfc(p1,p2)<<endl;
exit(0);
}