#include <fstream>
#include <algorithm>

#define x first
#define y second

using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

typedef pair<double, double> pct;

const int nMax=12e4+5;

int n, poz, top;
pct v[nMax], stiva[nMax];

double semn(const pct& a, const pct& b, const pct& c)
{
    return a.x*(b.y-c.y)+b.x*(c.y-a.y)+c.x*(a.y-b.y);
}

bool cmp(const pct& a, const pct& b)
{
    return semn(v[1], a, b) > 0;
}

int main()
{
    ios_base::sync_with_stdio(false);
    fin.tie(0);

    fin>>n;
    v[0].x=v[0].y=1e9+100, poz=0;

    for(int i=1; i<=n; i++)
    {
        fin>>v[i].x>>v[i].y;

        if(v[i].x < v[poz].x || (v[i].x==v[poz].x && v[i].y < v[poz].y))
            poz=i;
    }

    swap(v[1], v[poz]);
    sort(v+2, v+n+1, cmp);

    stiva[1]=v[1], stiva[2]=v[2];
    top=2;

    for(int i=3; i<=n; i++)
    {
        while(top>1 && semn(stiva[top-1], stiva[top], v[i])<0)
            top--;

        stiva[++top]=v[i];
    }

    fout<<top<<'\n';

    fout.precision(6);

    for(int i=1; i<=top; i++)
        fout<<fixed<<stiva[i].x<<' '<<stiva[i].y<<'\n';

    fin.close();
    fout.close();

    return 0;
}