#include <iostream>
#include <stdio.h>
#include <algorithm>
#include <fstream>
#include <iomanip>

using namespace std;

ifstream f2("infasuratoare.in");
ofstream g2("infasuratoare.out");
FILE*f=fopen("infasuratoare.in","r");
FILE*g=fopen("infasuratoare.out","w");

struct punct {
    double x,y;
}v[120005],A,B;

int comp(punct A, punct B)
{
    return (A.y<B.y || A.y==B.y && A.x<B.x);
}

int use[120005],st[120005],n,i,pas,k;

void coeficienti(punct A, punct B, double &aa, double &bb, double &cc)
{
    aa=A.y-B.y;
    bb=B.x-A.x;
    cc=A.x*B.y-A.y*B.x;
}

void modific()
{
    if (pas==1) {
        i++;
        if (i==n)
            pas=-1;
    }
    else i--;
}

int semn(punct A, punct B, punct C)
{
    double aa,bb,cc;
    coeficienti(A,B,aa,bb,cc);
    if (aa*C.x+bb*C.y+cc<=0) return -1;
    return 1;
}

int coliniar(punct A, punct B, punct C)
{
    double aa,bb,cc;
    coeficienti(A,B,aa,bb,cc);
    if (aa*C.x+bb*C.y+cc==0)
        return 0;
    return 1;
}

void acoperire()
{
    double u,umin,aa,bb,cc;
    sort(v+1,v+n+1,comp);
    pas=1;
    st[1]=1;
    st[2]=2;
    use[2]=1;
    k=2;    ///vf stivei
    i=2;    ///punctul
    while (i>1) {
            while (use[i])  ///parcurg punctele neselectate  si ma intorc
                modific();
            if (i==0) break;
            while (k>1 && (semn(v[st[k-1]],v[st[k]],v[i])==-1 || coliniar(v[st[k-1]],v[st[k]],v[i])==0)) {
                use[st[k]]=0;   ///scot din stiva si deselectez
                k--;
            }
            k++;
            st[k]=i;
            use[i]=1;
    }
    //fprintf(g,"%d%s",k-1,"\n");
    g2<<k-1<<'\n';
    for (i=1;i<k;i++)
        //fprintf(g,"%.6f%s%.6f%s",v[st[i]].x," ",v[st[i]].y,"\n");
        g2<<fixed<<setprecision(6)<<v[st[i]].x<<' '<<fixed<<setprecision(6)<<v[st[i]].y<<'\n';
}

int main()
{
f2>>n;
//fscanf(f,"%d",&n);
for (i=1;i<=n;i++)
    //fscanf(f,"%f%f",&v[i].x,&v[i].y);
    f2>>v[i].x>>v[i].y;
acoperire();
    return 0;
}