#include <fstream>
#include <algorithm>
#include <iomanip>
#include <stack>
#define DIM 120010
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
int n;
pair<double,double> v[DIM],aux;
int S[DIM];

double det(const pair<double,double> &a,const pair<double,double> &b,const pair<double,double> &c){
        return (a.first-c.first)*(b.second-c.second)-(b.first-c.first)*(a.second-c.second);
}

int cmp(const pair<double,double> &a,const pair<double,double> &b){
    return (det(v[1],a,b)>0);
}

int main(void){
    register int i,j,p,q,k;
    register double x,y;

    f>>n;
    p=1;
    for(i=1;i<=n;i++){
        f>>x>>y,v[i]=make_pair(x,y);
        if(v[p]>v[i])   p=i;
    }
    aux=v[p],v[p]=v[1],v[1]=aux;

    sort(v+2,v+n+1,cmp);

    S[1]=1,k=2,S[2]=2;
    for(i=3;i<=n;i++){
        while(k>1 && det(v[S[k]],v[S[k-1]],v[i])>=0)
            k--;
        S[++k]=i;
    }

    g<<k<<"\n";
    for(i=1;i<=k;i++){
        g<<setprecision(9)<<fixed<<v[S[i]].first<<" "<<v[S[i]].second<<"\n";
    }
    return 0;
}