#include <cstdio>



#include <algorithm>

#include <fstream>

#include <iomanip>



using namespace std;



#define x first

#define y second



typedef pair<double, double> Point;



ifstream fin("infasuratoare.in");

ofstream fout("infasuratoare.out");



const int MAX_N = 120005;



int n;

Point v[MAX_N];



Point stack[MAX_N];

int head;



void read() {

    fin >> n;

    for (int i = 1; i <= n; ++i)

        fin >> v[i].x >> v[i].y;

}



inline 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);

}



inline int cmp(const Point& p1, const Point& p2) {

    return cross_product(v[1], p1, p2) < 0;

}



void sort_points() {

    int pos = 1;

    for (int i = 2; i <= n; ++i)

        if (v[i] < v[pos])

            pos = i;

    swap(v[1], v[pos]);

    sort(v + 2, v + n + 1, cmp);

}



void convex_hull() {

    sort_points();



    stack[1] = v[1];

    stack[2] = v[2];

    head = 2;

    for (int i = 3; i <= n; ++i) {

        while (head >= 2 && cross_product(stack[head - 1], stack[head], v[i]) > 0)

            --head;

        stack[++head] = v[i];

    }

}



void write() {

    fout << fixed;

    fout << head << "\n";

    for (int i = head; i >= 1; --i)

        fout << setprecision(9) << stack[i].x << " " << stack[i].y << "\n";

}



int main() {

    read();

    convex_hull();

    write();

}