#include <bits/stdc++.h>
#define MAX 120120
#define INF 999999999
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
struct point
{
    double x,y;
} v[MAX];
double determ(point a,point b,point c)
{
    return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
}
bool compar(point a,point b)
{
    return determ(v[1],a,b)<0;
}
point st[MAX];
int n,xmin=INF,ymin=INF,start,vf;
int main()
{
    int i;
    fin>>n;
    for(i=1; i<=n; i++)
    {
        fin>>v[i].x>>v[i].y;
        if(v[i].x<xmin)
        {
            xmin=v[i].x;
            ymin=v[i].y;
            start=i;
        }
        else if(v[i].x==xmin&&v[i].y<ymin)
        {
            ymin=v[i].y;
            start=i;
        }
    }
    swap(v[start],v[1]);
    sort(v+2,v+n+1,compar);
    st[1]=v[1];
    st[2]=v[2];
    vf=2;
    for(i=3; i<=n; i++)
    {
        while(vf>=2&&determ(st[vf-1],st[vf],v[i])>0)
                vf--;
        st[++vf]=v[i];
    }
fout<<vf<<endl;
fout<<setprecision(6)<<fixed;
for(i=vf; i>=1;i--)
        fout<<st[i].x<<' '<<st[i].y<<endl;
    return 0;
}