#include <bits/stdc++.h>

using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
typedef long double ld;
int n;
struct point
{
    ld x,y;
} v[120005];
point start;
bool byx(point a, point b)
{
    if(a.x!=b.x)
        return a.x<b.x;
    return a.y<b.y;
}
ld aria(point a, point b,point c)
{
    a.x-=c.x;
    b.x-=c.x;
    a.y-=c.y;
    b.y-=c.y;
    return a.x*b.y-a.y*b.x;
}
bool egal(point a,point b)
{
    return a.x==b.x&&a.y==b.y;
}
bool comp(point a,point b)
{
    /*a.x-=start.x;
    a.y-=start.y;
    b.x-=start.x;
    b.y-=start.y;*/
    if(egal(a,start))
        return 1;
    if(egal(b,start))
        return 0;
    if(aria(a,b,start)<0)
        return 0;
    if(aria(a,b,start)>0)
        return 1;
    if(aria(a,b,start)==0)
        return a.x<b.x;
}
int main()
{
    ios_base::sync_with_stdio(false);
    fin.tie(0);
    fin>>n;
    for(int i=1;i<=n;i++)
        fin>>v[i].x>>v[i].y;
    sort(v+1,v+n+1,byx);
    start=v[1];
    sort(v+1,v+n+1,comp);
    vector<point> s;
    s.push_back(start);
    for(int i=2;i<=n;i++)
    {
        while(s.size()>=2)
        {
            int lg=s.size();
            if(aria(v[i],s[lg-1],s[lg-2])>0)
                s.pop_back();
            else
                break;
        }
        s.push_back(v[i]);
    }
    fout<<s.size()<<'\n';
    fout<<fixed<<setprecision(12);
    for(auto i:s)
        fout<<i.x<<' '<<i.y<<'\n';
    return 0;
}