#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#define NM 120010
#define INF 200000000
#define type double

using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

struct poz{type x,y;} V[NM];
int N,i,IND[NM],ST=0;
bool comp(int a,int b) {
    return atan2(V[a].y-V[ST].y,V[a].x-V[ST].x)>atan2(V[b].y-V[ST].y,V[b].x-V[ST].x);
}
int SK[NM],k=0;
bool right(int a,int b,int c) {
    return ((V[a].x*V[b].y+V[a].y*V[c].x+V[b].x*V[c].y-V[b].y*V[c].x-V[a].x*V[c].y-V[a].y*V[b].x)>0);
}
int main () {
    f >> N;V[0].x=V[0].y=INF;
    for (i=1;i<=N;i++) {
        f >> V[i].x >> V[i].y;
        if (V[i].x<V[ST].x || (V[i].x==V[ST].x && V[i].y<V[ST].y)) ST=i;
    }
    for (i=1;i<=N;i++)
        if (i!=ST) IND[++IND[0]]=i;
    sort(IND+1,IND+IND[0]+1,comp);
    SK[++k]=ST;
    for (i=1;i<=IND[0];i++) {
        if (IND[i]==ST) continue;
        while(k>=2 && right(SK[k-1],SK[k],IND[i]))
            k--;
        SK[++k]=IND[i];
    }
    g << k << '\n';
    g << fixed;
    for (i=k;i>=1;i--) g << setprecision(7) << V[SK[i]].x << ' ' << V[SK[i]].y << '\n';
    f.close();g.close();
    return 0;
}