#include <cstdio>
#include <cmath>
#include <algorithm>

using namespace std;

const double eps=1.0e-12;

struct POINT{
    double x,y;
};

POINT LL,p[120005];
int h[120005];

int CCW(POINT P1,POINT P2,POINT P3){
    double cp;
    cp=(1.0*P2.x-P1.x)*(1.0*P3.y-P2.y)-(1.0*P2.y-P1.y)*(1.0*P3.x-P2.x);
    if(fabs(cp)<eps){
        return 0;
    }else if(cp>=eps){
        return 1;
    }
    return -1;
}

bool cmp(POINT P1,POINT P2){
    if(CCW(LL,P1,P2)==1){
        return 1;
    }else{
        return 0;
    }
}

int main(){
    freopen("infasuratoare.in","r",stdin);
    freopen("infasuratoare.out","w",stdout);
    int n,i,top;
    scanf("%d",&n);
    scanf("%lf%lf",&p[0].x,&p[0].y);
    for(i=1;i<n;++i){
        scanf("%lf%lf",&p[i].x,&p[i].y);
        if(p[i].y-p[0].y<=-eps || (fabs(p[i].y-p[0].y)<eps && (p[i].x-p[0].x)<=-eps)){
            swap(p[0],p[i]);
        }
    }
    LL=p[0];
    sort(p+1,p+n,cmp);
    top=1;
    h[0]=0;
    h[1]=1;
    i=2;
    p[n]=p[0];
    while(i<=n){
        if(CCW(p[h[top-1]],p[h[top]],p[i])>0){
            h[++top]=i;
            i++;
        }else{
            top--;
        }
    }
    printf("%d\n",top);
    for(i=0;i<top;++i){
        printf("%lf %lf\n",p[h[i]].x,p[h[i]].y);
    }
    return 0;
}