#include<bits/stdc++.h>
using namespace std;


inline double det(pair<int,int> a,pair<int,int> b,pair<int,int> c)
{
    return a.first*b.second+b.first*c.second+c.first*a.second-c.first*b.second-a.first*c.second-b.first*a.second;
}

const int maxN=(120005);

pair<double,double> v[maxN];

bool cmp(pair<int,int> a,pair<int,int> b)
{
    return det(v[1],a,b)>0;
}

int n,st[maxN],vf;

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

    scanf("%d",&n);

    int p=1;

    for(int i=1;i<=n;i++)
    {
        scanf("%lf%lf",&v[i].first,&v[i].second);
        if(v[i].first<v[p].first || (v[i].first==v[p].first && v[i].second<v[p].second)) p=i;
    }

    swap(v[1],v[p]);

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


    st[++vf]=1;
    st[++vf]=2;

    for(int i=3;i<=n;i++)
    {
        while(vf>=2 && det(v[st[vf-1]],v[st[vf]],v[i])<0) vf--;

        st[++vf]=i;
    }

    printf("%d\n",vf);


    for(int i=1;i<=vf;i++)
        printf("%.12f %.12f\n",v[st[i]].first,v[st[i]].second);

    return 0;
}