#include<bits/stdc++.h>
using namespace std;
struct P{
double x,y;
}p[2001],s[2001];
int n,top;
inline double dis(P a,P b){
return (a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y);
}
inline P operator-(P a,P b){
return (P){a.x-b.x,a.y-b.y};
}
inline double operator*(P a,P b){
return a.x*b.y-b.x*a.y;
}
inline bool operator<(P a,P b){
double t=(a-p[1])*(b-p[1]);
if(t==0)return dis(a,p[1])<dis(b,p[1]);
return t<0;
}
inline void graham(){
int k=1;
for(int i=2;i<=n;i++)
i......
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