#include <bits/stdc++.h>

using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
int n,pozstart;
struct point
{
    double x;
    double y;
};
point v[200001],start,st[200001];
bool comp(point a,point b)
{
    a.x-=start.x;
    a.y-=start.y;
    b.x-=start.x;
    b.y-=start.y;
    if(a.x*b.y<a.y*b.x)
        return 1;
    else if(a.x*b.y==a.y*b.x&&a.x<b.x)
        return 1;
    return 0;
}
double aria(point a,point b,point c)
{
    a.x-=c.x;
    a.y-=c.y;
    b.x-=c.x;
    b.y-=c.y;
    return a.x*b.y-a.y*b.x;
}
void infasoara()
{
    start.x=1000000000;
    start.y=1000000000;
    pozstart=0;
    for(int i=1;i<=n;i++)
    {
        if(v[i].x<start.x)
        {
            start=v[i];
            pozstart=i;
        }
        else if(v[i].x==start.x&&v[i].y<start.y)
        {
            start=v[i];
            pozstart=i;
        }
    }
    for(int i=1;i<=n;i++)
        if(i==pozstart)
    {
        for(int j=i+1;j<=n;j++)
            v[j-1]=v[j];
        break;
    }
    n--;
    sort(v+1,v+n+1,comp);
    st[1]=start;
    st[2]=v[1];
    int lgst=2;
    for(int i=2;i<=n;i++)
    {
        while(aria(st[lgst-1],st[lgst],v[i])>0&&lgst>2)
            lgst--;
        st[++lgst]=v[i];
    }
    fout<<lgst<<'\n';
    for(int i=lgst;i>=1;i--)
        fout<<fixed<<setprecision(12)<<st[i].x<<" "<<st[i].y<<'\n';
}
int main()
{
    fin>>n;
    for(int i=1;i<=n;i++)
        fin>>v[i].x>>v[i].y;
    infasoara();
    return 0;
}