#include <bits/stdc++.h>
using namespace std;
ifstream fin ("infasuratoare.in");
ofstream fout("infasuratoare.out");
struct ceva
{
    double x,y;
}v[120010],s[120010];
int n,poz,i,lg;
int cross_product(ceva a,ceva b,ceva c)
{
    return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
}
int cmp(const ceva a,const ceva b)
{
    return cross_product(v[1],a,b)<0;
}
int main()
{
    fin>>n;
    for(i=1;i<=n;i++)
    {
        fin>>v[i].x>>v[i].y;
        if(poz==0 || (v[i].x<v[poz].x || ((v[i].x==v[poz].x & v[i].y<v[poz].y))))
            poz=i;
    }
    swap(v[1],v[poz]);
    sort(v+2,v+n+1,cmp);
    s[++lg]=v[1];
    s[++lg]=v[2];
    for(i=3;i<=n;i++)
    {
        while(lg>=2 && cross_product(s[lg-1],s[lg],v[i])>0)
            lg--;
        s[++lg]=v[i];
    }
    fout<<lg<<'\n';
    fout<<fixed;
    for(i=lg;i>=1;i--)
        fout<<setprecision(6)<<s[i].x<<" "<<s[i].y<<'\n';
    return 0;
}