#include <algorithm>
#include <stdio.h>
#include <iostream>
#include <vector>

#define x first
#define y second

using namespace std;

typedef pair<double, double> pct;

int N;

pct v[121010];
pct stiv[121010];

double signc(pct a,pct b,pct c){

    return (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);

}

int cmp(pct a, pct b){

    return signc(v[1],a,b)<0;

}

int k;

int main(){

    freopen("infasuratoare.in","r",stdin);
    freopen("infasuratoare.out","w",stdout);

    scanf("%d",&N);

    for(int i=1;i<=N;++i){
        scanf("%lf%lf",&v[i].x,&v[i].y);
    }
    int pos=1;
    for(int i=2;i<=N;++i){
        if(v[i]<v[pos]){
            pos = i;
        }
    }
    swap(v[pos],v[1]);

    sort(v+2,v+N+1,cmp);

    for(int i=1;i<=N;++i){
        while(k>=2 && signc(stiv[k-1],stiv[k],v[i]) > 0) --k;

        stiv[++k] = v[i];
    }
    printf("%d\n",k);

    for(int i=k;i>=1;--i){
        printf("%lf %lf\n",stiv[i].x,stiv[i].y);

    }

    return 0;
}