#include <fstream>
#include <iomanip>
#include <algorithm>
#include <vector>

using namespace std;

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

pair<double, double> A[120005];
int under[120005];
int top[120005];
bool used[120005];

long long det(pair<int, int> a1, pair<int, int> a2, pair<int, int> a3){
    return a1.first*a2.second + a2.first*a3.second + a3.first*a1.second - a2.second*a3.first - a3.second*a1.first - a1.second*a2.first;
}

int main()
{
    int n;
    cin>>n;
    for ( int i=1; i<=n; i++ ){
        double x, y;
        cin>>x;
        cin>>y;
        A[i].first=x;
        A[i].second=y;
    }
    for (int i=1; i<n; i++){
        for (int j=1; j<n-i+1; j++){
            if (A[j].second > A[j+1].second){
                swap(A[j], A[j+1]);
            }
            if (A[j].second == A[j+1].second && A[j].first > A[j+1].first){
                swap(A[j], A[j+1]);
            }
        }
    }
    int contdown=0;
    int last, beflast;
    for (int i=1; i<=n; i++){
        while (contdown > 1 && det(A[beflast], A[last], A[i])< 0){
            contdown--;
            last=under[contdown];
            beflast=under[contdown-1];
            used[last]=1;
        }
        contdown++;
        under[contdown]=i;
        beflast=last;
        last=i;
    }
    contdown--;
    //am facut partea de jos
    int contup=0;
    for (int i=n; i>=1; i--){
        while (contup > 1 && det(A[beflast], A[last], A[i])< 0){
            contup--;
            last=top[contup];
            beflast=top[contup-1];
            used[last]=1;
        }
        contup++;
        top[contup]=i;
        beflast=last;
        last=i;
    }
    contup--;
    //am facut partea de sus
    cout<<contdown+contup<<'\n';
    for (int i=1; i<=contdown; i++){
        cout<<setprecision(5)<<fixed<<A[under[i]].first<<" "<<A[under[i]].second<<'\n';
    }
    for (int i=1; i<=contup; i++){
        cout<<setprecision(5)<<fixed<<A[top[i]].first<<" "<<A[top[i]].second<<'\n';
    }
    return 0;
}