1 #include<cstdio> 2 #include<algorithm> 3 #include<cmath> 4 #include<iostream> 5 using namespace std; 6 #define EPS 0.000000000000001 7 #define N 1501 8 typedef long long ll; 9 typedef long double llf;10 llf sqr(const llf &x){return x*x;}11 struct Point12 {13     llf x,y;14     Point(const llf &a,const llf &b){x=a;y=b;}15     Point(){}16     void Read(){cin>>x>>y;}17 };18 typedef Point Vector;19 struct Line20 {21     Point l,r,m; llf len;22     Line(const Point &a,const Point &b){l=a;r=b;}23     Line(){}24     void Init(){m=Point((l.x+r.x)/2.0,(l.y+r.y)/2.0);len=sqrt(sqr(l.x-r.x)+sqr(l.y-r.y));}25 };26 bool Equal(const llf &a,const llf &b){return fabs(a-b)<EPS ? 1 : 0;}27 bool Less(const llf &a,const llf &b){return a-b<(-EPS) ? 1 : 0;}28 bool LeEqu(const llf &a,const llf &b){return a-b<EPS ? 1 : 0;}29 bool operator < (const Point &a,const Point &b)30 {return (!Equal(a.x,b.x))?Less(a.x,b.x):Less(a.y,b.y);}31 bool operator == (const Point &a,const Point &b)32 {return (Equal(a.x,b.x)&&Equal(a.y,b.y)) ? 1 : 0;}33 bool operator != (const Point &a,const Point &b){return a==b ? 0 : 1;}34 bool operator < (const Line &a,const Line &b)35 {return a.m!=b.m ? a.m<b.m : Less(a.len,b.len);}36 bool operator == (const Line &a,const Line &b)37 {return (Equal(a.len,b.len)&&a.m==b.m) ? 1 : 0;}38 bool operator != (const Line &a,const Line &b){return a==b ? 0 : 1;}39 Vector operator - (const Point &a,const Point &b){return Vector(a.x-b.x,a.y-b.y);}40 llf Cross(const Vector &a,const Vector &b){return a.x*b.y-a.y*b.x;}41 int n,m,head;42 Point p[N];43 llf ans;44 Line lines[N*N>>1];45 int main()46 {47     scanf("%d",&n);48     for(int i=1;i<=n;i++) p[i].Read();49     for(int i=1;i<=n;i++)50       for(int j=i+1;j<=n;j++)51         if(p[i]!=p[j])52           {53             lines[++m]=Line(p[i],p[j]);54             lines[m].Init();55           }56     sort(lines+1,lines+m+1);57     for(int i=1;i<=m;i++)58       {59         if(lines[i]!=lines[i-1]) head=i;60         if(lines[i]!=lines[i+1])61           if(i-head)62             {63               for(int j=head;j<=i;j++)64                 for(int k=j+1;k<=i;k++)65                   ans=max(ans,fabs(Cross(lines[j].l-lines[j].m,lines[k].l-lines[k].m))66                   +fabs(Cross(lines[j].l-lines[j].m,lines[k].r-lines[k].m)));67             }68       }69     printf("%lld\n",(ll)ans);70     return 0;71 }