#include <bits/stdc++.h>

using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
const int lim=12e4+10;
int i,n,k;
struct punct
{
    double x,y;
}v[lim],s[lim];

bool comp1(punct a,punct b)
{
    return ((a.x<b.x)||(a.x==b.x&&a.y<b.y));
}
bool comp2(punct a,punct b)
{
    return ((double)(a.y-v[1].y)*(b.x-v[1].x)<(double)(b.y-v[1].y)*(a.x-v[1].x));
}
double determinant(double x,double y,double x2,double y2,double x3,double y3)
{
    return (x*y2+x2*y3+x3*y-x*y3-x2*y-x3*y2);
}
int main()
{
    fin>>n;
    for(i=1;i<=n;i++)
        fin>>v[i].x>>v[i].y;
    sort(v+1,v+n+1,comp1);
    s[1].x=v[1].x;s[1].y=v[1].y;

    sort(v+2,v+n+1,comp2);
    s[2].x=v[2].x;s[2].y=v[2].y;
    k=2;
    for(i=3;i<=n;i++)
    {
        k++;
        s[k].x=v[i].x;
        s[k].y=v[i].y;
        double d=determinant(s[k-2].x,s[k-2].y,s[k-1].x,s[k-1].y,s[k].x,s[k].y);
        while(k>2&&d<0)
        {
            k--;
            s[k].x=v[i].x;
            s[k].y=v[i].y;
            d=determinant(s[k-2].x,s[k-2].y,s[k-1].x,s[k-1].y,s[k].x,s[k].y);
        }
    }
    fout<<k<<'\n';
    for(i=1;i<=k;i++)
        fout<<fixed<<setprecision(6)<<s[i].x<< " "<<s[i].y<<'\n';
    return 0;
}