#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <stack>
#include <cmath>
#include <iomanip>

struct Point {
    Point() = default;

    Point(double x, double y) : x(x), y(y) {}

    double x = 0, y = 0;

    inline friend std::istream &operator>>(std::istream &istream, Point &point) {
        return istream >> point.x >> point.y;
    }

    inline friend std::ostream &operator<<(std::ostream &ostream, const Point &p) {
        return ostream << p.x << " " << p.y;
    }


    static double cross_product(const Point &A, const Point &B, const Point &C) {
        return (B.x - A.x) * (C.y - A.y) - (B.y - A.y) * (C.x - A.x);
    }
};

bool check(std::stack<Point> &stack, const Point &cnd) {
    Point p1 = stack.top();
    stack.pop();
    Point p2 = stack.top();
    stack.push(p1);

    return Point::cross_product(p2, p1, cnd) > 0;
}

int main() {
    std::ifstream input("infasuratoare.in");
    std::ofstream output("infasuratoare.out");

    int n;

    input >> n;
    std::vector<Point> points(n);
    for (int i = 0; i < n; ++i) {
        input >> points[i];
    }

    int pos = 0;
    for (int i = 1; i < n; ++i) {
        if (points[i].x < points[pos].x || (points[i].x == points[pos].x && points[i].y < points[pos].y)) {
            pos = i;
        }
    }
    std::swap(points[0], points[pos]);
    Point ref = points[0];

    std::sort(points.begin() + 1, points.end(), [ref](const Point &lhs, const Point &rhs) {
        double cp = Point::cross_product(ref, lhs, rhs);
        if (cp == 0) {
            double dx1 = lhs.x - ref.x;
            double dy1 = lhs.y - ref.y;
            double dx2 = rhs.x - ref.x;
            double dy2 = rhs.y - ref.y;
            return (dx1 * dx1 + dy1 * dy1) < (dx2 * dx2 + dy2 * dy2);
        }
        return cp > 0;
    });

    std::stack<Point> stack;
    stack.push(points[0]);
    stack.push(points[1]);

    for (int i = 2; i < n; ++i) {
        while (stack.size() >= 2) {
            Point p1 = stack.top();
            stack.pop();
            Point p2 = stack.top();
            if (Point::cross_product(p2, p1, points[i]) > 0) {
                stack.push(p1);
                break;
            }
        }
        stack.push(points[i]);
    }

    output << stack.size() << "\n";
    output << std::setprecision(12) << std::fixed;
    std::vector<Point> result;
    while (!stack.empty()) {
        result.push_back(stack.top());
        stack.pop();
    }
    std::reverse(result.begin(), result.end());
    for (const auto &p : result) {
        output << p << '\n';
    }

    return 0;
}