#include <bits/stdc++.h>

using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
struct punct
{
    long double x,y;
} p[120001];
inline long double det (punct a, punct b, punct c)
{
    return (b.x-a.x)*(c.y-a.y)-(c.x-a.x)*(b.y-a.y);
}
bool comp (punct a, punct b)
{
    return det (p[1], a, b) > 0;
}
int s[120001];
int main()
{
    int n,i,min1=1;
    fin>>n;
    for(i=1; i<=n; i++)
    {
        fin>>p[i].x>>p[i].y;
        if(p[i].y<p[min1].y||(p[i].y==p[min1].y&&p[i].x<p[min1].x))min1=i;
    }
    swap(p[1],p[min1]);
    sort(p+2,p+n+1,comp);
    s[0]=2;
    s[1]=1;
    s[2]=2;
    for(i=3; i<=n; i++)
    {
        while(s[0]>=2&&det(p[s[s[0]-1]],p[s[s[0]]],p[i])<=0)s[0]--;
        s[++s[0]]=i;
    }

    fout<<fixed<<setprecision(15);
    fout<<s[0]<<'\n';
    for(i=1; i<=s[0]; i++)fout<<p[s[i]].x<<" "<<p[s[i]].y<<'\n';
    return 0;
}