#include <bits/stdc++.h>

using namespace std;

ifstream f("data.in");
ofstream g("data.out");

struct punct {double x;double y;}p[120003];
punct s[120003];

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

bool cmp(punct i,punct j)
{
    double d;
    d=determinant(p[1],i,j);
    if(d>0)return 1;
    else return 0;
}

int i,j,n;

int main()
{
    f>>n;
    f>>p[1].x>>p[1].y;
    j=1;
    for(int i=2;i<=n;i++)
    {
        f>>p[i].x>>p[i].y;
        if(p[i].x<p[j].x ||(p[i].y<p[j].y&&p[i].x<p[j].x)) j=i;
    }
    swap(p[1],p[j]);
    sort(p+2,p+n+1,cmp);
    int k=2;
    s[1]=p[1];s[2]=p[2];
    for(int i=3;i<=n;i++)
    {
        while(k>1&&determinant(s[k-1],s[k],p[i])<0)k--;
        k++;
        s[k]=p[i];
    }
    g<<k<<'\n';
    g<<fixed;
    for(int i=1;i<=k;i++)
        g<<setprecision(6)<<s[i].x<<' '<<setprecision(6)<<s[i].y<<'\n';
    f.close();g.close();
}