#include<stdio.h>
#include<stdlib.h>
typedef struct { double x,y; }P;
P v[120005],r,w[120005];
int s[120005],h,n,i,p;
int A(const void *a,const void *b) {
    P *c=(P*)a,*d=(P*)b;
    return c<d;
}
double C(P o,P a,P b) { return (a.x-o.x)*(b.y-o.y)-(b.x-o.x)*(a.y-o.y); }
int main() {
    freopen("infasuratoare.in","r",stdin),freopen("infasuratoare.out","w",stdout),scanf("%d",&n);
    for(p=i=1;i<=n;i++)
        scanf("%lf%lf",&v[i].x,&v[i].y),p=v[i].x<v[p].x||(v[i].x==v[p].x&&v[i].x<v[p].x)?i:p;
    r=v[1],v[1]=v[p],v[p]=r,s[++h]=1;
    for(i=1;i<n;i++)
        w[i]=v[i+1];
    qsort(w,n-1,sizeof(w),A);
    for(i=2;i<=n;i++)
        v[i]=w[i-1];
    for(i=2;i<=n;i++) {
        for(;h>1&&C(v[s[h-1]],v[s[h]],v[i])>0;h--);
        s[++h]=i;
    }
    printf("%d\n",h);
    for(i=h;i;i--)
        printf("%.6lf %.6lf\n",v[s[i]].x,v[s[i]].y);
}