#include <fstream>
#include <algorithm>
using namespace std;
int n, i, j, k, pminim;
struct punct {
    double first, second;
};
punct v[120001], s[120001];
ifstream fin ("infasuratoare.in");
ofstream fout ("infasuratoare.out");
double det (int X1, int Y1, int X2, int Y2, int X3, int Y3) {
    return (X2-X1)*(Y3-Y1)-(X3-X1)*(Y2-Y1);
}
int cmp (punct &a, punct &b)
{
    int d=det(0, 0, a.first, a.second, b.first, b.second);
    if (d!=0)
        return d>0;
    else
        return a.first*a.first+a.second*a.second > b.first*b.first+b.second*b.second;
}
int main () {
    fin>>n;
    pminim=0;
    v[0].first=v[0].second=1.0*1000000001;
    for (i=1;i<=n;i++) {
        fin>>v[i].first>>v[i].second;
        if (v[i].second<v[pminim].second || ( (v[i].second==v[pminim].second && v[i].first<v[pminim].first) ))
            pminim=i;
    }
    v[0]=v[pminim];
    v[pminim]=v[1];
    v[1]=v[0];
    for (i=1;i<=n;i++) {
        v[i].first-=v[0].first;
        v[i].second-=v[0].second;
    }
    sort(v+2, v+n+1, cmp);

    for (j=3;j<=n;j++) {
        if (det(v[1].first, v[1].second, v[2].first, v[2].second, v[j].first, v[j].second)!=0)
            break;
    }

    i=2;
    j--;
    while (i<j) {
        swap(v[i], v[j]);
        i++;
        j--;
    }
    s[1]=v[1];
    s[2]=v[2];
    k=2;
    for (j=3;j<=n;j++) {
        while (k>=2 && det(s[k-1].first, s[k-1].second, s[k].first, s[k].second, v[j].first, v[j].second)<0) {
            k--;
        }
        s[++k]=v[j];
    }
    fout<<k<<"\n";
    for (i=1;i<=k;i++) {
        fout<<s[i].first+v[0].first<<" "<<s[i].second+v[0].second<<"\n";
    }
    return 0;
}