#include<fstream>
#include<algorithm>
#include<iomanip>
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
struct punct {
    double x; double y;
};
punct p[120001], st[120001];
int n, i, j, varf;
double prod (punct p0, punct p1, punct p2){
        return (p1.x - p0.x) * (p2.y - p0.y) - (p1.y - p0.y) * (p2.x - p0.x);
}

int cmp (punct p1, punct p2){
    return prod(p[1], p1, p2) < 0;
}

void infas(){
    st[1] = p[1]; st[2] = p[2]; varf = 2;
    for (i = 3; i <= n; ++i){
        while (varf >= 2 and prod(st[varf - 1], st[varf], p[i]) > 0)
            varf--;
        st[++varf] = p[i];
    }
    fout << fixed;
    fout << varf << '\n';
    for (i = varf; i >= 1; i--)
        fout << setprecision(9) << st[i].x << " " << st[i].y << '\n';
}

int main(){
    fin >> n;
    for (int i = 1; i <= n; i++)
        fin >> p[i].x >> p[i].y;
    int poz = 1;
    for (i =  1; i <= n; i++){
        if (p[i].x < p[poz].x)
            poz = i;
        else if (p[i].x == p[poz].x and p[i].y < p[poz].y)
            poz = i;
    }
    swap(p[1], p[poz]);
    sort(p + 2, p + n + 1, cmp);
   // for (i = 1; i <= n; i++)
   //     fout << p[i].x << " " << p[i].y << '\n';
    infas();
}