#include <bits/stdc++.h>

using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

const int nmax = 120005;
int n, z;

struct Point{
    double x, y;
}v[nmax], s[nmax];

double Area(Point a, Point b, Point c){
    return a.x*b.y + b.x*c.y + c.x*a.y -
           b.y*c.x - c.y*a.x - a.y*b.x;
}

bool cmp(Point a, Point b){
    return Area(v[1], a, b) > 0;
}

int main(){
    fin >> n;
    for (int i = 1; i <= n; ++i){
        fin >> v[i].x >> v[i].y;
    }
    Point start = v[1];
    int index = 1;
    for (int i = 2; i <= n; ++i){
        if (v[i].y < start.y){
            start = v[i];
            index = i;
        }
        else if (v[i].y == start.y && v[i].x < start.x){
            start = v[i];
            index = i;
        }
    }
    swap(v[index], v[1]);
    sort(v + 2, v + n + 1, cmp);
    stack <int> stiva;
    s[++z] = v[1];
    s[++z] = v[2];
    for (int i = 3; i <= n; ++i){
        while (z >= 2 && Area(s[z - 1], s[z], v[i]) < 0){
            --z;
        }
        s[++z] = v[i];
    }
    fout << z << "\n";
    fout << fixed << setprecision(6);
    for (int i = 1; i <= z; ++i){
        fout << s[i].x << " " << s[i].y << "\n";
    }
    fin.close();
    fout.close();
    return 0;
}