#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream cin("infasuratoare.in");
ofstream cout("infasuratoare.out");

#define pp pair <double, double>
#define x first
#define y second

pp p[120010];
int n,i,st[120010];

double det(pp a, pp b, pp c)
{
    return (a.x*b.y + b.x*c.y + c.x*a.y - a.y*b.x - b.y*c.x - c.y*a.x);
}

int main()
{
    cin>>n;
    for(i=1;i<=n;i++)
    {
        cin>>p[i].x>>p[i].y;
    }
    sort(p+1,p+n+1);

    st[0]=2; ///varful stivei
    st[1]=1;
    st[2]=2;
    for(i=3;i<=n;i++)
    {
        while(st[0]>=2 && det(p[st[st[0]-1]], p[st[st[0]]], p[i]) > 0)
            st[0]--;
        st[++st[0]]=i;
    }
    for(i=n-1;i>=1;i--)
    {
        while(det(p[st[st[0]-1]], p[st[st[0]]], p[i]) > 0)
            st[0]--;
        st[++st[0]]=i;
    }

    ///for(i=1;i<=st[0]-1;i++)
        ///cout<<p[st[i]].x<<" "<<p[st[i]].y<<'\n';

    cout<<st[0]-1<<'\n';
    for(i=st[0]-1;i>=1;i--)
        cout<<setprecision(6)<<fixed<<p[st[i]].x<<" "<<p[st[i]].y<<'\n';

    return 0;
}