#include <bits/stdc++.h>

using namespace std;

struct dot{
    double x;
    double y;
};
dot t[120000],stck[120000];
double f(dot a, dot b, dot c)
{
    return (b.x - a.x)*(c.y - a.y) - (c.x - a.x)*(b.y - a.y);
}
bool cmp(dot a, dot b)
{
    return (f(t[1],a,b) < 0);
}

int n,i,poz,st=1000000001,js=1000000001;

int main() 
{
    ifstream cin("infasuratoare.in");
    ifstream cout("infasuratoare.out");
    cin>>n;
    for (i=1; i<=n; i++)
        cin>>t[i].x>>t[i].y;
    for (i=1; i<=n; i++)
    {
        if (t[i].x<st) st=t[i].x,js=t[i].y,poz=i; else
        if (t[i].x==st) if (t[i].y<js) js=t[i].y,poz=i;
    }
    swap(t[1],t[poz]);
    sort(t+2,t+n+1,cmp);
    stck[1]=t[1];
    stck[2]=t[2];
    int last=2;
    for (i=3; i<=n; i++)
    {
        while (last>=2 && f(stck[last-1],stck[last],t[i])>0) last--;
        last++;
        stck[last]=t[i];
    }
    cout<<last<<'\n';
    for (i=last-1; i>=1; i--)
    cout<<setprecision(12)<<fixed<<stck[i].x<<" "<<stck[i].y<<'\n';
    cout<<setprecision(12)<<fixed<<stck[last].x<<" "<<stck[last].y<<'\n';
}