#include <cstdio>
#include <algorithm>
#include <cmath>

#define inFILE "infasuratoare.in"
#define outFILE "infasuratoare.out"
#define x first
#define y second

#define Nmax 120005

using namespace std;
pair<double,double> pct[Nmax];
pair<double,double> stak[Nmax],P;
int N,vf=2;

double cross_prod(pair<double,double> A,pair<double,double> B, pair<double,double> C)
{
    return A.x*B.y + B.x*C.y + C.x*A.y -
           A.y*B.x - B.y*C.x - C.y*A.x;
}
double dist(pair<double,double> A, pair<double,double> B)
{
    return sqrt( (A.x-B.x)*(A.x-B.x) + (A.y-B.y)*(A.y-B.y) );
}

class cmp{
public:
    bool operator()(const pair<double,double>A,const pair<double,double>B)const
    {
        if(pct[1].y - A.y == 0 && pct[1].y - B.y == 0 ||
           pct[1].x - A.y == 0 && pct[1].y - B.y == 0)
                return (dist(pct[1],A) < dist(pct[1],B));
        return cross_prod(pct[1],A,B) < 0;
    }
};

void read()
{
    scanf("%d",&N);
    for(int i = 1; i <= N; ++i)
        scanf("%lf%lf",&pct[i].x,&pct[i].y);
    int pz = 1;
    for(int i = 2; i <= N; ++i)
        if(pct[i] < pct[pz])
            pz = i;
    swap(pct[pz],pct[1]);
}

void make_hull()
{
    sort(pct+2,pct+N+1,cmp());
    stak[1] = pct[1];
    stak[2] = pct[2];
    for(int i = 3; i <= N; ++i)
    {
        while(vf >= 2 && cross_prod(stak[vf-1],stak[vf],pct[i]) > 0)
            --vf;
        stak[++vf] = pct[i];
    }
}

void print()
{
    printf("%d\n",vf);
    for(int i = vf; i >= 1; --i)
        printf("%.6lf %.6lf\n",stak[i].x,stak[i].y);
}

int main()
{
    freopen (   inFILE, "r", stdin );
    freopen (   outFILE, "w", stdout );

    read();
    make_hull();
    print();

    return 0;
}