#include <fstream>
#include <algorithm>
#include <iomanip>
#define nmax 130005
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
int n,k;
struct punct{double x;double y;};
punct v[nmax],s[nmax];

double deter(const punct &a,const punct &b,const punct &c)
{
    return (b.x-a.x) *(c.y-a.y) - (c.x-a.x) * (b.y-a.y);
}
bool cmp(const punct &a,const punct &b)
{
    return deter(v[1],a,b)>0;
}

int main()
{
    int i,j,p;
    f>>n;
    for (i=1;i<=n;i++)
        f>>v[i].x>>v[i].y;
    p=1;
    for (i=2;i<=n;i++)
        if (v[i].y<v[p].y||(v[i].y==v[p].y&&v[i].x<v[i].x))
            p=i;
    swap(v[1],v[p]);

    sort(v+2,v+n+1,cmp);
    s[++k]=v[1];
    s[++k]=v[2];
    for (i=3;i<=n;i++) {
        while (k>=2&&deter(s[k-1],s[k],v[i])<0)
                k--;
        s[++k]=v[i];
    }
    g<<k<<'\n';
    for (i=1;i<=k;i++)
        g<<setprecision(9)<<fixed<<s[i].x<<' '<<s[i].y<<'\n';
    return 0;
}