#include <fstream>
#include <vector>
#include <algorithm>
#include <iomanip>

using namespace std;

struct Point {
    double x, y;
    bool operator<(const Point& p) const {
        return x < p.x || (x == p.x && y < p.y);
    }
    bool operator==(const Point& p) const {
        return x == p.x && y == p.y;
    }
};

double cross(const Point& O, const Point& A, const Point& B) {
    return (A.x - O.x) * (B.y - O.y) - (A.y - O.y) * (B.x - O.x);
}

vector<Point> convex_hull(vector<Point> points) {
    int n = points.size(), k = 0;
    vector<Point> hull(2 * n);
    sort(points.begin(), points.end());
    for (int i = 0; i < n; ++i) {
        while (k >= 2 && cross(hull[k-2], hull[k-1], points[i]) <= 0) k--;
        hull[k++] = points[i];
    }
    for (int i = n-2, t = k+1; i >= 0; --i) {
        while (k >= t && cross(hull[k-2], hull[k-1], points[i]) <= 0) k--;
        hull[k++] = points[i];
    }
    hull.resize(k-1);
    return hull;
}

int main() {
    ifstream fin("infasuratoare.in");
    ofstream fout("infasuratoare.out");
    fout << fixed << setprecision(6);

    int n;
    fin >> n;
    vector<Point> points(n);
    for (int i = 0; i < n; ++i) {
        fin >> points[i].x >> points[i].y;
    }

    vector<Point> hull = convex_hull(points);
    fout << hull.size() << '\n';
    for (const auto& p : hull) {
        fout << p.x << ' ' << p.y << '\n';
    }

    fin.close();
    fout.close();
    return 0;
}