#include <cstdio>
#include <algorithm>
#define nmax 125000
using namespace std;
struct punct{double x;double y;};
punct p[nmax],s[nmax];
int n,k;

double deter(const punct &a,const punct &b,const punct &c)
{
    return (b.x-a.x)*(c.y-a.y)-(c.x-a.x)*(b.y-a.y);
}
bool cmp(const punct &a,const punct &b)
{
    return deter(p[1],a,b)>0;
}
int main()
{
    freopen("infasuratoare.in","r",stdin);
    freopen("infasuratoare.out","w",stdout);
    int i,j=1;
    scanf("%d",&n);
    for (i=1;i<=n;i++) {
        scanf("%lf %lf",&p[i].x,&p[i].y);
        if (p[i].y<p[j].y||(p[i].y==p[j].y&&p[i].x<p[j].x))
            j=i;
    }
    swap(p[1],p[j]);
    sort(p+2,p+n+1,cmp);
    s[++k]=p[1];
    s[++k]=p[2];
    for (i=3;i<=n;i++) {
        while (k>=2&&deter(s[k-1],s[k],p[i])<0)
            k--;
        s[++k]=p[i];
    }
    printf("%d\n",k);
    for (i=1;i<=k;i++) {
        printf("%.6lf %.6lf\n",s[i].x,s[i].y);
    }
    return 0;
}