#include <algorithm>
#include <iomanip>
#include <fstream>
#define x first
#define y second
#define MAX_N  120005
using namespace std;
typedef pair<double, double> Point;
const double EPS = 1e-12;//10^(-12)
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
int n,p,i;
Point v[MAX_N];
bool vis[MAX_N];
int st[MAX_N], head;
double prod(Point O, Point A, Point B) {
    return (A.x - O.x) * (B.y - O.y) - (B.x - O.x) * (A.y - O.y);
}
int main()
{
    f>> n;
    for ( i = 1; i <= n; ++i)
        f >> v[i].x >> v[i].y;
    sort(v + 1, v + n + 1);

    st[1] = 1; st[2] = 2; head = 2;
    vis[2] = true;

    for (i = 1, p = 1; i > 0; i +=p )
    {
        if(i==n) p=-1;
        if (vis[i]) continue;
        while (head >= 2 && prod(v[st[head - 1]], v[st[head]], v[i]) < EPS)
            vis[st[head--]] = false;
        st[++head] = i;
        vis[i] = true;
    }
    g << head - 1 << "\n";
    g << setprecision(6) << fixed;
    for (int i = 1; i < head; ++i)
        g<< v[st[i]].x << ' ' << v[st[i]].y << "\n";
}