//#include <iostream>
#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;

ifstream cin("infasuratoare.in");
ofstream cout("infasuratoare.out");

pair<double,double> v[120005];
int hull[120005];

int cross_product(pair<int,int> P1,pair<int,int> P2,pair<int,int> P3){
    return (P1.first-P2.first)*(P1.second-P3.second)-(P1.second-P2.second)*(P1.first-P3.first);
}

int aria(pair<int,int> a,pair<int,int> b,pair<int,int> c){
    int a1=a.first,
    a2=a.second,
    b1=b.first,
    b2=b.second,
    c1=c.first,
    c2=c.second;
    return a1*b2+b2*c2+c1*a2-b2*c1-c2*a1-a2*b1;
}

bool ms(pair<int,int> a,pair<int,int> b){
    return (cross_product(v[1],a,b)>=0);
}

int main(){
    int mini=1,n;
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>v[i].first>>v[i].second;
        if(v[mini].second>v[i].second)
            mini=i;
    }
    swap(v[1],v[mini]);
    sort(v+2,v+n+1,ms);
    v[++n]=v[1];
    hull[1]=1;
    int cnt=1;
    for(int i=1;i<=n;i++){
        while(cnt>1 and cross_product(v[hull[cnt-1]],v[hull[cnt]],v[i])<=0){
            cnt--;
        }
        hull[++cnt]=i;
    }
    cnt--;
    cout<<cnt<<"\n";
    for(int i=1;i<=cnt;i++){
        cout<<fixed<<setprecision(6);
        cout<<v[hull[i]].first<<" "<<v[hull[i]].second<<"\n";
    }
}