#include<bits/stdc++.h>
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
const double eps=1.e-14;
const int NMAX=120000;
struct POINT
{
    double x,y;
};
POINT P[NMAX+5],LL;
int h[NMAX+5];
double cp(POINT P1,POINT P2,POINT P3)
{
    return (P2.x-P1.x)*(P3.y-P2.y)-(P2.y-P1.y)*(P3.x-P2.x);
}
int ccw(POINT P1,POINT P2,POINT P3)
{
    double product;
    product=cp(P1,P2,P3);
    if(fabs(product)<eps)
        return 0;
    if(product>=eps)
        return 1;
    return -1;
}
bool cmp(POINT A,POINT B)
{
    if(ccw(LL,A,B)==-1)
        return 0;
    else
        return 1;
}
int main()
{
    int n,i,r,top;
    fin>>n;
    fin>>P[1].x>>P[1].y;
    for(i=2;i<=n;i++)
    {
        fin>>P[i].x>>P[i].y;
        if(fabs(P[i].y-P[1].y)<eps&&(P[i].x-P[1].x<=-eps))
            swap(P[1],P[i]);
        else if(P[i].y-P[1].y<=-eps)
            swap(P[1],P[i]);
    }
    LL=P[1];
    sort(P+2,P+n+1,cmp);
    P[n+1]=LL;
    /*for(i=1;i<=n+1;i++)
        fout<<P[i].x<<" "<<P[i].y<<"\n";*/
    i=3;
    h[1]=1;h[2]=2;top=2;
    while(i<=n+1)
    {
        if(ccw(P[h[top-1]],P[h[top]],P[i])==-1)
            top--;
        else
        {
            h[++top]=i;
            i++;
        }
    }
    fout<<fixed<<showpoint;
    fout<<top-1<<"\n";
    for(i=1;i<top;i++)
        fout<<setprecision(6)<<P[h[i]].x<<" "<<P[h[i]].y<<"\n";
    return 0;
}