#include <bits/stdc++.h>
#define x first
#define y second
#define punct pair<double,double>
using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

const int N_MAX=120010;

punct v[N_MAX];
punct stiva[N_MAX];

int N,varf;

double determin(punct a,punct b,punct c)
{
    return (c.y-a.y)*(b.x-a.x)-(b.y-a.y)*(c.x-a.x);
}

int crit(const punct p1,const punct p2)
{
    return determin(v[1],p1,p2)<0;
}

void convex()
{
    int poz=1;
    for(int i=2;i<=N;i++)
    {
        if(v[i]<v[poz])poz=i;
    }
    swap(v[1],v[poz]);
    sort(v+1,v+N+1,crit);
    stiva[1]=v[1];
    stiva[2]=v[2];
    varf=2;
    for(int i=3;i<=N;i++)
    {
        while(varf>2 && determin(stiva[varf-1],stiva[varf],v[i])<0)
            varf--;
        stiva[++varf]=v[i];
    }
}

int main()
{
    fin>>N;
    for(int i=1;i<=N;i++)fin>>v[i].x>>v[i].y;
    convex();
    fout<<varf<<'\n';
    for(int i=varf;i>=1;i--)
    {
        fout<<fixed<<setprecision(6)<<stiva[i].x<<' '<<stiva[i].y<<'\n';
    }
    return 0;
}