#include <iostream>
#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
#define x first
#define y second
const double EPS=1e-12;
#define MAX 120010
#define cout fout
typedef double d;

d cross_product(pair<d, d> O, pair<d, d> A, pair<d, d> B)
{
    return (A.x - O.x) * (B.y - O.y) - (A.y - O.y) * (B.x - O.x);
}

pair<d, d> a[MAX];
int dr, viz[MAX], st[MAX];

int main()
{
    int n, i;
    fin >> n;
    for(i = 1 ; i <= n ; i++)
    {
        fin >> a[i].x >> a[i].y;
    }
    sort(a + 1, a + n + 1);

    st[1] = 1; st[2] = 2;
    viz[2] = 1;
    dr = 2;

    for(i = 1 ; i <= n ; i++)
    {
        if(viz[i])
            continue;
        while(dr >= 2 && cross_product(a[st[dr - 1]], a[st[dr]], a[i]) < EPS)
            viz[st[dr--]] = 0;
        st[++dr] = i;
        viz[i] = 1;
    }
    for(i = n ; i >= 1 ; i--)
    {
        if(viz[i])
            continue;
        while(dr >= 2 && cross_product(a[st[dr - 1]], a[st[dr]], a[i]) < EPS)
            viz[st[dr--]] = 0;
        st[++dr] = i;
        viz[i] = 1;
    }
    cout << dr - 1 << "\n";
    cout << setprecision(6) << fixed;
    for(i = 1 ; i < dr ; i++)
        cout << a[st[i]].x << " " << a[st[i]].y << "\n";
}