#include <fstream>
#include <algorithm>
#include <cmath>
#include <iomanip>
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
const double eps=1.0e-12;
struct POINT
{
    double x,y;
};
const int NMAX=120000;
POINT P[NMAX+5];
POINT LL;
int h[NMAX+5];
double cp(POINT A, POINT B, POINT C)
{
    return (B.x - A.x) * (C.y - B.y) - (B.y - A.y) * (C.x - B.x);
}
int ccw(POINT A, POINT B, POINT C)
{
    /*0 daca abc sunt coliniare
      1 daca c este in sens trigonometric fata de ab (la stanga)
      -1 daca este in sens orar fata de ab (la dreapta)
    */

    double cpp = cp(A, B, C);

    if(fabs(cpp) < eps)
        return 0;
    if(cpp >= eps)
        return 1;
    return -1;
}

bool cmp(POINT A, POINT B)
{
    return ccw(LL,A,B)>0;
}
int main()
{
    int n, i, top;
    double tx, ty;
    fin >> n;
    fin >> tx >> ty;
    LL.x=tx;
    LL.y=ty;
    P[0]=LL;
    for(i=1; i<n; ++i)
    {
        fin >> tx >> ty;
        P[i].x=tx;
        P[i].y=ty;

        if(LL.y-ty>eps || fabs(LL.y-ty)<eps && LL.x-tx>eps)
        {
            P[i]=LL;
            LL.x=tx;
            LL.y=ty;
            P[0]=LL;
        }

    }
    sort(P+1,P+n,cmp);
    P[n]=LL;
    h[0]=0;
    h[1]=1;
    top=1;
    i=2;
    while(i<=n)
    {
        if(ccw(P[h[top-1]],P[h[top]],P[i])>0)
        {
            h[++top]=i;
            i++;
        }
        else
            top--;
    }
    fout << top << "\n";
    fout << showpoint << fixed << setprecision(6);
    for(i=0; i<top; ++i)
        fout << P[h[i]].x << " " << P[h[i]].y << "\n";

    fin.close();
    fout.close();
    return 0;
}