#include <bits/stdc++.h>

using namespace std;

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

struct ura{
    double x,y;
    int unde;
}v[120001],cap1,cap2;

bool cmp(ura a, ura b){
    if(a.x<b.x)
        return true;
    if(a.x>b.x)
        return false;
    if(a.y<b.y)
        return true;
    if(a.y>b.y)
        return false;
}


double determinant(ura a, ura b, ura c){
    return (a.x*b.y+b.x*c.y+c.x*a.y-b.x*a.y-c.x*b.y-a.x*c.y);
}

int stiva[120001];
int main()
{
    int n,i,k,k2;
    in>>n;
    for(i=1;i<=n;++i)
        in>>v[i].x>>v[i].y;
    sort(v+1,v+n+1,cmp);
    cap1=v[1];
    cap2=v[n];
    for(i=2;i<n;++i)
        if(determinant(cap1,cap2,v[i])<0)
            v[i].unde=1;
        else
            v[i].unde=-1;
    stiva[1]=1;
    k=1;
    for(i=2;i<=n;++i)
        if(v[i].unde==1||v[i].unde==0)
    {
        while(k>1&&determinant(v[stiva[k-1]],v[stiva[k]],v[i])<0)
            --k;
        stiva[++k]=i;
    }
    stiva[k]=n;
    k2=k;
    for(i=n-1;i>=1;--i){
        if(v[i].unde==-1||v[i].unde==0)
        {
            while(k2>k&&determinant(v[stiva[k2-1]],v[stiva[k2]],v[i])<0)
                --k2;
            stiva[++k2]=i;
        }
    }
    out<<k2-1<<'\n';
    for(i=1;i<=k2-1;++i)
        out<<fixed<<setprecision(6)<<v[stiva[i]].x<<" "<<v[stiva[i]].y<<'\n';
    return 0;
}