#include <iostream>
#include <fstream>
#include <iomanip>
#include <algorithm>
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
int n,i,k;
struct xoy{
double x,y;
}a[120005];
double det(xoy a,xoy b,xoy c)
{return a.x*b.y+b.x*c.y+a.y*c.x-c.x*b.y-b.x*a.y-c.y*a.x;
}
bool comp(xoy z, xoy t)
{return det(a[1],z,t)>0;
}

int main()
{f>>n>>a[1].x>>a[1].y;
double mn=a[1].x;
int mni=1;
for(i=2;i<=n;i++)
    {f>>a[i].x>>a[i].y;
    if(a[i].x<mn)mn=a[i].x,mni=i;
    else if(a[i].x==mn)
        {if(a[i].y<a[mni].y)
            mni=i;
        }
    }
swap(a[1],a[mni]);
sort(a+2,a+n+1,comp);
a[n+1]=a[1];
int k=2;
for(i=3;i<=n+1;i++)
    {while(k>=2 && det(a[k-1],a[k],a[i])<0)k--;
    a[++k]=a[i];
    }
g<<k-1<<'\n';
for(i=2;i<=k;i++)
    g<<fixed<<setprecision(6)<<a[i].x<<" "<<a[i].y<<'\n';
return 0;
}