#include <iostream>
#include <algorithm>
#include <fstream>
#include <iomanip>

using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

struct Punct{double x,y;};
Punct v[120000],rez[120000];
int n,i,k;

bool p(Punct p, Punct p1)
{
    return p.y<p1.y?true:p.y==p1.y?p.x<p1.x?true:false:false;
}
int semn(Punct a,Punct b,Punct c)
{
if((b.x-a.x)*(c.y-a.y)-(c.x-a.x)*(b.y-a.y)>=0)
    return 1;
else
    return 0;
}
int main()
{
f>>n;

for(i=1;i<=n;i++)
f>>v[i].x>>v[i].y;

sort(v+1,v+n+1,p);

rez[1]=v[1];
k=1;

for(i=2;i<=n;i++)
{
while(k > 1 && !semn(rez[k-1], rez[k], v[i]))
k--;
rez[++k]=v[i];
}
for(i=n-1;i>=1;i--)
{
while(!semn(rez[k-1], rez[k], v[i]))
k--;
rez[++k]=v[i];
}

g<<k-1<<endl;
g<<fixed;
g<<setprecision(6);
for(i=1;i<=k-1;i++)
g<<rez[i].x <<" "<<rez[i].y<<endl;
f.close();
g.close();
return 0;
}