//#include <iostream>
#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream cin("infasuratoare.in");
ofstream cout("infasuratoare.out");
struct Point{;
    double x,y;
}v[120005],hull[120005];
double Cross_Product(Point a,Point b,Point c){
    return (a.x-b.x)*(a.y-c.y)-(a.y-b.y)*(a.x-c.x);
}
bool ms(Point a,Point b){
    return (Cross_Product(v[1],a,b)>=0);
}
int main(){
    int n,mini=1,cnt=0;
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>v[i].x>>v[i].y;
        if(v[mini].y>v[i].y){
            mini=i;
        }
    }
    swap(v[1],v[mini]);
    sort(v+2,v+n+1,ms);
    v[++n]=v[1];
    hull[++cnt]=v[1];
    for(int i=2;i<=n;i++){
        while(cnt>=2){
            if(Cross_Product(hull[cnt-1],hull[cnt],v[i])<=0){
                cnt--;
            }
            else
                break;
        }
        hull[++cnt]=v[i];
    }
    cnt--;
    cout<<cnt<<"\n";
    for(int i=1;i<=cnt;i++){
        cout<<fixed<<setprecision(6)<<hull[i].x<<" "<<hull[i].y<<"\n";
    }
    return 0;
}