#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <algorithm>
#include <set>
#include <map>
#include <cmath>
#include <cstring>
#include <iomanip>
using namespace std;

#define fi first
#define se second
typedef long long LL;
typedef long double LD;

struct point{
    LD x,y;
};

int N; point a[120100];

LD area(point A, point B, point C){
    return (A.x*B.y+B.x*C.y+C.x*A.y-A.y*B.x-B.y*C.x-C.y*A.x);
}

vector<point> gethull(){
   sort(a+1,a+N+1,[](point A, point B) { return A.x < B.x; });
    point dhull[130000],uhull[130000];
    point cr=a[1];
    int i,usz=0,dsz=0;

    for (i=2; i<=N; i++){
        if (cr.y>=a[i].y) uhull[++usz]=cr;
        else dhull[++dsz]=cr;

        cr=a[i];
        while (usz>1 && area(cr,uhull[usz],uhull[usz-1])<=0) usz--;
        while (dsz>1 && area(cr,dhull[dsz],dhull[dsz-1])>=0) dsz--;
    }

    vector<point> res(0);
    for (i=1; i<=dsz; i++)
        res.push_back(dhull[i]);
    res.push_back(cr);
    for (i=usz; i>0; i--)
        res.push_back(uhull[i]);
    return res;
}
int main(){
    ifstream fin("infasuratoare.in");
    ofstream fout("infasuratoare.out");
    fin >> N;

    int i;
    for (i=1; i<=N; i++)
        fin >> a[i].x >> a[i].y;

    vector<point> ans(0);
    ans = gethull();
    fout << fixed << setprecision(9);

    fout << ans.size() << "\n";
    for (point P : ans)
        fout << P.x << " " << P.y << "\n";


    return 0;
}