#include <iostream>
#include <fstream>
#include <algorithm>
#include <iomanip>

using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

struct point{double x, y;} v[120005],q[120005];
int n;

double produs(const point& A, const point& B, const point& C)
{
    return (B.x-A.x)*(C.y-A.y)-(B.y-A.y)*(C.x-A.x);
}

bool cmp(const point& p1, const point& p2)
{
    return produs(v[1],p1,p2)<0;
}

void sortare()
{
    int pos=1;
    for(int i=2;i<=n;i++)
        if((v[i].x<v[pos].x)||(v[i].x==v[pos].x&&v[i].y<v[pos].y))
           pos=i;
    swap(v[1],v[pos]);
    sort(v+2,v+n+1,cmp);
}

int main()
{
    f>>n;
    for(int i=1;i<=n;i++)
        f>>v[i].x>>v[i].y;
    sortare();
    q[1]=v[1];
    q[2]=v[2];
    int  k=2;
    for(int i=3;i<=n;i++)
    {   while(k>=2&&produs(q[k-1],q[k],v[i])>0)
            --k;
        q[++k]=v[i];
    }
    g<<fixed;
    g<<k<<'\n';
    for(int i=k;i>=1;--i)
        g<<setprecision(9)<<q[i].x<<' '<<q[i].y<<'\n';
    return 0;
}