#include <fstream>
#include <algorithm>
#include <iomanip>
#define DIM 120010
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
int n, m, i, j, k, st[DIM], ind;

struct punct{
    double x, y;
} a[DIM], x, aux;

double afla(punct a, punct b, punct c){
    return (b.x-a.x)*(c.y-a.y)-(c.x-a.x)*(b.y-a.y);
}

bool cmp(punct a, punct b){
    double p1=b.x*a.y;
    double p2=a.x*b.y;
    if(p1<p2)
        return 1;
    return 0;
}

int main(){
    x.x=1000000010;
    x.y=1000000010;
    f>>n;
    for(i=1; i<=n; i++)
    {
        f>>a[i].x>>a[i].y;
        if(a[i].y<x.y || (a[i].y==x.y && a[i].x<x.x))
            x=a[i], ind=i;
    }
    aux=a[ind];
    a[ind]=a[1];
    a[1]=aux;
    for(i=1; i<=n; i++)
        a[i].x-=x.x, a[i].y-=x.y;
    sort(a+2, a+n+1, cmp);
    st[1]=1;
    st[2]=2;
    k=2;
    for(i=3; i<=n; i++)
    {
        while(k>=2 && afla(a[ st[k-1] ], a[ st[k] ], a[i])<0)
            k--;
        st[++k]=i;
    }
    g<<k<<"\n"<<fixed;
    for(i=1; i<=k; i++)
        g<<setprecision(6)<<a[ st[i] ].x+x.x<<' '<<a[ st[i] ].y+x.y<<"\n";
    return 0;
}