#include <fstream>
#include <algorithm>
#include <vector>
#include <math.h>
#include <iomanip>
#define EPSILON 0.000000001
using namespace std;

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

struct punct
{
    double x, y;
    bool operator !=(punct other)
    {
        return fabs(x - other.x)>EPSILON || fabs(y - other.y)>EPSILON;
    }
} pcte[120005];

double orientation(punct a, punct b, punct c)
{
    return (b.y-a.y)*(c.x-a.x) - (c.y-a.y)*(b.x-a.x);
}

int n, start;

bool cmp(punct a, punct b)
{
    double o = orientation(pcte[start], a, b);
    if(o < 0)
        return true;
    return false;
}

void read()
{
    f>>n;
    f>>pcte[0].x>>pcte[0].y;
    for(int i = 1; i<n; ++i)
    {
        f>>pcte[i].x>>pcte[i].y;
        if(pcte[start].x > pcte[i].x || (pcte[start].x == pcte[i].x && pcte[start].y > pcte[i].y))
        {
            start = i;
        }
    }
    swap(pcte[start], pcte[0]);
    start = 0;
    sort(pcte+1, pcte+n, cmp);
}

punct S[120005];
int len = 0;

void solve()
{
    for(int index = 0; index < n; ++index)
    {
        while(len >= 2 && orientation(S[len-1], pcte[index], S[len-2]) > 0)
        {
            len--;
        }
        S[len++] = pcte[index];
    }
}

void print()
{
    g<<len<<"\n";
    for(int i = 1; i<len; ++i)
    {
        g<<fixed<<setprecision(6)<<S[i].x<<" "<<S[i].y<<"\n";
    }
    g<<fixed<<setprecision(6)<<S[0].x<<" "<<S[0].y<<"\n";
}

int main()
{
    read();
    solve();
    print();
    return 0;
}