#include <iostream>
#include <fstream>
#include <algorithm>
#include <iomanip>
#define NMAX 120005
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
int n,na=0,nb=0,top=0,nrp;
struct coord {
    double x,y;
} v[NMAX],a[NMAX],b[NMAX],downp,upp,stiva[NMAX];

double 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 cmp1(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;
}
bool cmp2(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];
    }

    for(int i=1; i<=n; i++)
        if(aria(downp,upp,v[i])==-1)
            a[++na]=v[i];
        else if(aria(downp,upp,v[i])==1)
            b[++nb]=v[i];
    sort(a+1,a+na+1,cmp1);
    sort(b+1,b+nb+1,cmp2);

    stiva[++top]=downp;
    for(int i=1; i<=na; i++)
        if(top==1)
            stiva[++top]=a[i];
        else {
            if(aria(stiva[top-1],stiva[top],a[i])==0)
                stiva[top]=a[i];
            else {
                while(aria(stiva[top-1],stiva[top],a[i])!=1 && top>1)
                    top--;
                stiva[++top]=a[i];
            }
        }
    while(aria(stiva[top-1],stiva[top],upp)!=1 && top>1)
            top--;
    nrp=top;

    stiva[++top]=upp;
    for(int i=1; i<=nb; i++)
        if(top-nrp==1)
            stiva[++top]=b[i];
        else {
            while(aria(stiva[top-1],stiva[top],b[i])!=1 && top-nrp>1)
                top--;
            if(aria(stiva[top-1],stiva[top],b[i])==0)
                stiva[top]=b[i];
            else
                stiva[++top]=b[i];
        }
    while(aria(stiva[top-1],stiva[top],downp)!=1 && top-nrp>1)
            top--;
    nrp=top;

    fout<<setprecision(6)<<fixed;
    fout<<nrp<<'\n';
    for(int i=1; i<=nrp; i++)
        fout<<stiva[i].x<<" "<<stiva[i].y<<'\n';
    return 0;
}