#include <iostream>
#include <cstdio>
#include <vector>
#include <queue>
#include <algorithm>
#include <bitset>
#include <iomanip>

#define eps 1e-12

using namespace std;

int n,l=2,l1=2;
double x, y;
vector <pair<int,int>> pct;
vector <int> q, q1;
bitset <120005> viz;

double det(int p1, int p2, int p3)
{
    return (pct[p2].first-pct[p1].first)*(pct[p3].second-pct[p1].second) - (pct[p2].second-pct[p1].second)*(pct[p3].first-pct[p1].first);
}

int main()
{
    freopen("infasuratoare.in","r",stdin);
    freopen("infasuratoare.out","w",stdout);

    cin>>n;
    for(int i=0; i<n; ++i)
    {
        cin>>x>>y;
        pct.push_back({x,y});
    }
    sort(pct.begin(),pct.end());

    q.push_back(0);
    q.push_back(1);
    viz[1]=1;

    for(int i=2; i<n; ++i)
    {
        if(viz[i])
            continue;
        while(q.size()>1 && det(q[l-2],q[l-1],i)<eps)
            --l, viz[q[l]]=0, q.pop_back();
        q.push_back(i);
        ++l;
        viz[i]=1;
    }

    for(int i=n-1; i>=0; --i)
    {
        if(viz[i])
            continue;
        while(q.size()>1 && det(q[l-2],q[l-1],i)<eps)
            --l, viz[q[l]]=0, q.pop_back();
        q.push_back(i);
        ++l;
        viz[i]=1;
    }

    cout<<l-1<<"\n";
    q.erase(q.begin());

    cout<<fixed<<setprecision(6);

    for(int i : q)
        cout<<pct[i].first<<" "<<pct[i].second<<"\n";

    return 0;
}