#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
#define C(i,n) for(int i=0;i<n;i++)
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
int n;
struct P{double x,y;}v[120003],s[120003];
bool  o( P a,P b, P c){return ( (b.x - a.x) *(c.y - a.y) - (c.x - a.x) * (b.y - a.y) >= 0);}
void G()
{
    int t=1;
    C(i,n)if(v[i].y<v[0].y || v[i].y<v[0].y && v[i].x < v[0].x)swap(v[0],v[i]);
   sort(v+1,v+n,[=](P a,P b){ return o(v[0],a,b);});
   s[1] = v[0];
   C(i,n){
       while( t >= 2 && !o(s[t-1],s[t],v[i+1]) )
           t--;
       s[++t] = v[i+1];
   }
   g<<--t<<'\n';
   C(i,t)g<<setprecision(12)<<fixed<<s[i+1].x<<" "<<s[i+1].y<<'\n';
}
int main()
{
    f>>n;
    C(i,n)f>>v[i].x>>v[i].y;
    G();
    return 0;
}