#include <iostream>
#include <fstream>
#include <algorithm>
#include <iomanip>
#define NMAX 120005
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
int n,topl,topr;
struct coord {
    double x,y;
} v[NMAX],downp,upp,stl[NMAX],str[NMAX];

int aria(coord a,coord b,coord c) {
    double arie=a.x*(b.y-c.y)-b.x*(a.y-c.y)+c.x*(a.y-b.y);
    if(arie>0)
        return 1;
    else if(arie<0)
        return -1;
    return 0;
}
bool cmp(coord x,coord y) {
    if(x.y<y.y) return 1;
    else if(x.y==y.y && x.x<y.x) return 1;
    else return 0;
}
int main() {
    fin>>n;
    downp.x=downp.y=2000000000;
    upp.y=upp.x=-1000000000;
    for(int i=1; i<=n; i++) {
        fin>>v[i].x>>v[i].y;
        if(v[i].y<downp.y || (v[i].y==downp.y && v[i].x<downp.x))
            downp=v[i];
        if(v[i].y>upp.y || (v[i].y==upp.y && v[i].x>upp.x))
            upp=v[i];
    }
    sort(v+1,v+n+1,cmp);

    topl=topr=1;
    stl[topl]=v[1];
    str[topr]=v[1];
    for(int i=2; i<=n; i++)
        if(aria(downp,upp,v[i])==1) {///left
            while(aria(stl[topl-1],stl[topl],v[i])!=-1 && topl>1)
                topl--;
            stl[++topl]=v[i];
        } else if(aria(downp,upp,v[i])==-1) { ///right
            while(aria(str[topr-1],str[topr],v[i])!=1 && topr>1)
                topr--;
            str[++topr]=v[i];
        }

    fout<<setprecision(6)<<fixed;
    fout<<topr+topl<<'\n';
    for(int i=1; i<=topl; i++)
        fout<<stl[i].x<<" "<<stl[i].y<<'\n';
    fout<<upp.x<<" "<<upp.y<<'\n';
    for(int i=topr;i>1;i--)
        fout<<str[i].x<<" "<<str[i].y<<'\n';
    return 0;
}