#include<fstream>
#include<algorithm>
#include<iostream>
#include<iomanip>
#define x first
#define y second
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
const int DN=12e4+5;
typedef pair<double,double> pii;
int n,top,stk[DN];
pii a[DN];
double det(pii A,pii B,pii C)
{
    double rez;
    rez=B.x*C.y+C.x*A.y+A.x*B.y;
    rez-=A.y*B.x+B.y*C.x+C.y*A.x;
    return rez;
}
void infas()
{
    sort(a+1,a+n+1);
    top=2;
    stk[1]=1;
    stk[2]=2;
    for(int i=3;i<=n;i++)
    {
        while(top>1&&det(a[i],a[stk[top-1]],a[stk[top]])<0)
            top--;
        top++;
        stk[top]=i;
       // cout<<top<<'\n';
    }

    for(int i=n-1;i>0;i--)
    {
        while(top>1&&det(a[i],a[stk[top-1]],a[stk[top]])<0)
            top--;
        top++;
        stk[top]=i;
    }
    fout<<top-1<<'\n';
    for(int i=1;i<top;i++)
        fout<<fixed<<setprecision(12)<<a[stk[i]].x<<' '<<a[stk[i]].y<<'\n';
    for(int i=2;i<top;i++)
        if(det(a[stk[i-1]],a[stk[i]],a[stk[i+1]])<0)
            while(1);
}
int main()
{
    fin>>n;
    for(int i=1;i<=n;i++)
    	fin>>a[i].x>>a[i].y;
    infas();
}