#include <bits/stdc++.h>
#define x first
#define y second
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
typedef pair<double,double> p;
p v[140006];
int d[140005];
int poz,n,i,k;
double det(p a,p b,p c){
    return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
}
bool cmp(p a,p b){
   return det(v[1],a,b)>=0;
}
int main()
{
    fin>>n;
    p minn;
    minn.x=inf;
    minn.y=inf;
    for(i=1;i<=n;i++){
        fin>>v[i].x>>v[i].y;
        if(minn>v[i]){
            minn=v[i];
            poz=i;
        }
    }
    swap(v[1],v[poz]);
    sort(v+2,v+n+1,cmp);
    d[1]=1;
    d[2]=2;
    k=2;
    for(i=3;i<=n;i++){
        while(k>=2 && det(v[d[k-1]],v[d[k]],v[i]) <=0){
            k--;
        }
        k++;
        d[k]=i;
    }
    fout<<k<<"\n";
    for(i=1;i<=k;i++)
        fout<<setprecision(7)<<fixed<<v[d[i]].x<<" "<<v[d[i]].y<<"\n";
}