#include <bits/stdc++.h>

using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

struct pct
{
    double first,second;
} a[120005];
double det(pct z,pct x, pct y)
{
    return(z.first*x.second+x.first*y.second+y.first*z.second-x.second*y.first-y.second*z.first-z.second*x.first);
}
bool comp(pct x,pct y)
{
    return det(a[1],x,y)>0;
}
int main()
{
    int n;
    int i;
    int mn;
    fin>>n;
    fin>>a[1].first>>a[1].second;
    mn=1;

    for(i=2; i<=n; i++)
    {
        fin>>a[i].first>>a[i].second;
        if(a[i].first<a[mn].first||(a[i].first==a[mn].first&&a[i].second<a[mn].second))mn=i;

    }
    swap(a[mn],a[1]);
    sort(a+2,a+n+1,comp);
    a[n+1]=a[1];
    n++;
    int l=2;
    for(i=3; i<=n; i++)
    {
        while(l>=2&&det(a[l-1],a[l],a[i])<0)l--;
        a[++l]=a[i];
    }
    fout<<l-1<<'\n';
    for(i=1; i<l; i++)
    {
        fout<<fixed<<setprecision(12)<<a[i].first<<" "<<a[i].second<<'\n';
    }
    return 0;
}