#include<fstream>
#include<algorithm>
#include<vector>
#define INF 999999999
std::ifstream fin("infasuratoare.in");
std::ofstream fout("infasuratoare.out");
struct point{
    double x, y;
};
int n;
std::vector<point>v;
inline double det(point a, point b, point c)
{
    return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
}
bool cmp(const point &a, const point &b){
    point aux={0, 0};
    double d=det(aux, a, b);
    return (d>0);
};
int main()
{
    point s[120005];
    int k=0, pmin;
    fin>>n;
    v=std::vector<point>(n+5);
    v[0]={INF, INF};
    for(int i=1; i<=n; ++i)
    {
        fin>>v[i].x>>v[i].y;
        if(v[i].y<v[pmin].y || (v[i].y==v[pmin].y && v[i].x<v[pmin].x))
            pmin=i;
    }
    v[0]=v[pmin];
    v[pmin]=v[1];
    v[1]=v[pmin];
    for(int i=1; i<=n; ++i)
    {
        v[i].x-=v[0].x;
        v[i].y-=v[0].y;
    }
    std::sort(v.begin()+2, v.begin()+n+1, cmp);
    s[1]=v[1];
    s[2]=v[2];
    k=2;
    for(int i=3; i<=n; ++i)
    {
        while(k>=2 && det(s[k-1], s[k], v[i])<0)
            --k;
        s[++k]=v[i];
    }
    fout<<k<<'\n';
    for(int i=1; i<=k; ++i)
        fout<<s[i].x+v[0].x<<' '<<s[i].y+v[0].y<<'\n';
    return 0;
}