#include <bits/stdc++.h>

using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
struct bln
{
    double x,y;
}v[120005];
int n,mn,i;
int det(bln a,bln b,bln c)
{
    return (a.x-b.x)*(a.y-c.y)-(a.y-b.y)*(a.x-c.x);
}
bool comp(bln a,bln b)
{
    return det(v[1],a,b)>0;
}
int main()
{
    f>>n;
    f>>v[1].x>>v[1].y;
    mn=1;
    for(i=2;i<=n;i++)
    {
        f>>v[i].x>>v[i].y;
        if(v[i].x<v[mn].x|| (v[i].x==v[mn].x && v[i].y<v[mn].y))
            mn=i;
    }
    swap(v[mn],v[1]);
    sort(v+2,v+n+1,comp);
    int k=2;
    v[n+1]=v[1];
    for(i=3;i<=n+1;i++)
    {
        while(k>=2 && det(v[k-1],v[k],v[i])<0) k--;
        v[++k]=v[i];
    }
    g<<k-1<<'\n';
    for(i=1;i<k;i++)
        g<<fixed<<setprecision(6)<<v[i].x<<" "<<v[i].y<<'\n';
    return 0;
}