#include <bits/stdc++.h>

using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

long double cx=INT_MAX,cy=INT_MAX;

struct punct
{
    long double x,y;
}v[120100],st[120100];

int compare(punct A,punct B)
{
    return (atan2(A.x-cx,A.y-cy) > atan2(B.x-cx,B.y-cy));
}

int semn(long double val)
{
    if(val==0)return 0;
    else if(val>0)return -1;
    else return 1;
}

int viraj_dreapta(punct A,punct B,punct C)
{
    return (semn(A.x*B.y + B.x*C.y + A.y*C.x - B.y*C.x - A.x*C.y - A.y*B.x));
}

int n,poz,i,t;
int main()
{
    f>>n;
    for(i=1;i<=n;i++)
    {
        f>>v[i].x>>v[i].y;

        if(v[i].x<cx)
        {
            cx=v[i].x;
            cy=v[i].y;
            poz=i;
        }
        else if(v[i].x==cx)
        {
            if(v[i].y<cy)
            {
                cy=v[i].y;
                poz=i;
            }
        }
    }

    swap(v[1],v[poz]);
    sort(v+2,v+n+1,compare);

    t=2;
    st[1]=v[1];
    st[2]=v[2];

    for(i=3;i<=n;i++)
    {
        while(t>2 && viraj_dreapta(st[t-1],st[t],v[i])==1)t--;
        t++;
        st[t]=v[i];
    }

    g<<t<<'\n';
    for(i=1;i<=t;i++)
    {
        g<<fixed<<setprecision(12)<<st[i].x<<" " <<fixed<<setprecision(12)<<st[i].y<<'\n';
    }
    return 0;
}