#include<bits/stdc++.h>
#define int long long
using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

int n,stiva[120005],viz[120005];

struct punct
{
    double x,y;
}v[120005];

int cmp(punct a, punct b)
{
    if(a.x==b.x)
        return a.y<b.y;
    return a.x<b.x;
}

double calculam(punct a, punct b, punct c)
{
    if((b.y-a.y)*(c.x-a.x)>=(c.y-a.y)*(b.x-a.x))
        return 1;
    return 0;
}

signed main()
{
    int i,prim,pas;
    f>>n;
    for(i=1;i<=n;i++)
        f>>v[i].x>>v[i].y;
    sort(v+1,v+n+1,cmp);
    stiva[1]=1;
    stiva[2]=2;
    prim=2;
    viz[2]=1;
    i=3;
    pas=1;
    while(viz[1]==0)
    {
        if(viz[i]==0)
        {
            while(prim>=2 && calculam(v[stiva[prim-1]],v[stiva[prim]],v[i])==1)
            {
                viz[stiva[prim]]=0;
                prim--;
            }
            viz[i]=1;
            prim++;
            stiva[prim]=i;
        }
        if(i==n)
            pas=-1;
        i+=pas;
    }
    prim--;
    g<<prim<<'\n';
    for(i=1;i<=prim;i++)
        g<<fixed<<setprecision(12)<<v[stiva[i]].x<<" "<<fixed<<setprecision(12)<<v[stiva[i]].y<<'\n';
    return 0;
}