#include <bits/stdc++.h>
#define Lmax 120002

using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
struct punct
{
    int x,y;
} a[Lmax],s[Lmax];
int n,i,k;
bool cmp(punct a, punct b)
{
    if(a.x < b.x || (a.x == b.x && a.y < b.y)) return true;
    return false;
}
int det(punct a,punct b, punct c)
{
    if((a.x-c.x)*(b.y-c.y)-(b.x-c.x)*(a.y-c.y)>=0)
        return 1;
    return 0;
}
int main()
{
    fin>>n;
    for (i=1; i<=n; i++)
        fin>>a[i].x>>a[i].y;
    sort(a+1,a+n+1,cmp);
    s[1]=a[1];
    k=1;
    for (i=2; i<=n; i++)
    {
        while (k>1&&!det(s[k-1],s[k],a[i]))
            k--;
        k++;
        s[k]=a[i];
    }
    for (i=n-1; i>=1; i--)
    {
        while (!det(s[k-1],s[k],a[i]))
            k--;
        k++;
        s[k]=a[i];
    }
    fout<<setprecision(6)<<fixed;
    fout<<k-1<<"\n";
    for(i=1; i<=k-1; i++) fout<<s[i].x<<" "<<s[i].y<<"\n";
    return 0;
}