> #include<iostream>
> #include<cmath>
> #include<algorithm>
> using namespace std;
> const int MAX=50005;
> struct point
> {
>    double x,y;     
> };
> point points[MAX],res[MAX];
> 
> bool mult(const point sp,const point ep,const point op)
> {
>     return (sp.x-op.x)*(ep.y-op.y)>=(ep.x-op.x)*(sp.y-op.y);     
> }
> 
> bool operator < (const point &l, const point r)
> {
>      return l.y<r.y||(l.y==r.y&&l.x<r.x);
> }
> 
> double dis(point a, point b)
> {
>        return (a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y);
> }
> int graham(point pnt[], int n, point res[])
> {
>     int i,len,k=0,top=1;
>     sort(pnt, pnt+n );
>     if(n==0)return 0; res[0]=pnt[0];
>     if(n==1)return 1; res[1]=pnt[1];
>     if(n==2)return 2; res[2]=pnt[2];
>     for(i=2; i<n; i++)
>     {
>              while(top&&mult(pnt[i],res[top],res[top-1]))
>                  top--;
>              res[++top]=pnt[i];
>     }
>     len=top;  res[++top]=pnt[n-2];
>     for(i=n-3; i>=0; i--)
>     {
>                while(top!=len&&mult(pnt[i],res[top],res[top-1]))
>                top--;
>                res[++top]=pnt[i];
>     }
>     return top;
> }
> 
> int main()
> {
>     int n;
>     cin>>n;
>     for(int i=0; i<n; i++)
>             cin>>points[i].x>>points[i].y;
>     
>     int top=graham(points, n, res);
>     double ans=0;
>     
>     for(int i=0; i<top; i++)
>     for(int j=i+1; j<top; j++)
>             if(dis(res[i],res[j])>ans)ans=dis(res[i],res[j]);
>     cout<<int(ans+0.0005)<<endl;
>     system("pause");
>     return 0;
> }