#include<fstream>
#include<cstdio>
#include<set>
#include<stack>
#include<vector>
#include<algorithm>
#define FOR(a,b,c) for(int a=b;a<=c;++a)
#include<cstring>
#include<bitset>
#include<cmath>
#include<iomanip>
#include<queue>
#define f cin
#define g cout
#define mp make_pair
#define pb push_back
#define x first
#define y second
#define ll long long
#define bit 20
#define inf (1<<30)
#define base 256
#define ba 255
#define N 500100
#define EPS 1e-12
#define mod  666013
#define inu "infasuratoare.in"
#define outu "infasuratoare.out"
using namespace std;
ifstream f(inu);
ofstream g(outu);
//int dx[]={0,0,0,1,-1};
//int dy[]={0,1,-1,0,0};
pair<double , double> v[N];
int t,s[N],n,viz[N];
double det(int a,int b,int c)
{
    double d=(v[a].x*v[b].y+v[b].x*v[c].y+v[a].y*v[c].x)-(v[b].y*v[c].x+v[a].y*v[b].x+v[a].x*v[c].y);
    return d;
}
int main ()
{
    f>>n;
    FOR(i,1,n)
        f>>v[i].x>>v[i].y;
    sort(v+1,v+n+1);
    s[1]=1;
    s[2]=2;
    t=2;
    viz[2]=1;
    FOR(i,3,n)
    {
        while(t>1&&det(s[t-1],s[t],i)<EPS)
        {
            viz[s[t]]=0;
            t--;
        }
        s[++t]=i;
        viz[i]=1;
    }
    for(int i=n-1;i>=1;--i)
    {
        if(!viz[i])
        {
            while(t>1&&det(s[t-1],s[t],i)<EPS)
            {
                viz[s[t]]=0;
                t--;
            }
            s[++t]=i;
        }
    }
    g<<t-1<<"\n";
    g<<setprecision(6)<<fixed;
    FOR(i,1,t-1)
    g<<v[s[i]].x<<" "<<v[s[i]].y<<"\n";
    return 0;
}