#include<cstdio>
#include<algorithm>
using namespace std;
struct pct{
    double x;
    double y;
}v[150000];
int n,i,j,st[150000],nr,pmin;
double xmin,ymin,auxx,auxy;
FILE *f,*g;
int verif(pct a,pct b,pct c){
    double x=(a.x-c.x)*(b.y-c.y)-(a.y-c.y)*(b.x-c.x);
    if(x<0.000000000001)
        return 1;
    return 0;
}
int cmp(pct a,pct b){
    return verif(a,b,v[1]);
}
int main(){
    f=fopen("infasuratoare.in","r");
    g=fopen("infasuratoare.out","w");
    fscanf(f,"%d",&n);
    xmin=ymin=1000000000;
    for(i=1;i<=n;i++){
        fscanf(f,"%lf%lf",&v[i].x,&v[i].y);
        if(v[i].x<xmin) {
            xmin=v[i].x;
            pmin=i;
        }
        else if(xmin==v[i].x&&v[i].y<v[pmin].y)
            pmin=i;
    }
    auxx=v[1].x;
    auxy=v[1].y;
    v[1].x=v[pmin].x;
    v[1].y=v[pmin].y;
    v[pmin].x=auxx;
    v[pmin].y=auxy;
    sort(v+2,v+n+1,cmp);
    st[1]=n;
    st[2]=n-1;
    nr=2;
    for(i=n-2;i>=1;i--){
        while(verif(v[st[nr-1]],v[st[nr]],v[i])==1&&nr>=1)
            nr--;
        st[++nr]=i;
    }
    fprintf(g,"%d\n",nr);
    for(i=1;i<=nr;i++){
        fprintf(g,"%.6lf %.6lf\n",v[st[i]].x,v[st[i]].y);
    }

    fclose(f);
    fclose(g);
    return 0;
}