#include<cstdio>
#include<algorithm>

#define Point pair<double,double>
#define x first
#define y second

using namespace std;
const int NMAX = 120005;
int N,i,Min,Cnt,St[NMAX];
Point P[NMAX];

double CrossProduct(Point A,Point B,Point C)
{
    return A.x*B.y+B.x*C.y+C.x*A.y-A.y*B.x-B.y*C.x-C.y*A.x;
}

bool cmp(Point A,Point B)
{
    return CrossProduct(P[1],A,B)<0;
}

int main()
{
    freopen("infasuratoare.in","r",stdin);
    freopen("infasuratoare.out","w",stdout);
    scanf("%d",&N); Min=1;
    for(i=1;i<=N;i++)
    {
        scanf("%lf",&P[i].x);
        scanf("%lf",&P[i].y);
        if(P[i]<P[Min]) Min=i;
    }
    swap(P[Min],P[1]); sort(P+2,P+N+1,cmp);

    St[1]=1; St[2]=2; Cnt=2;
    for(i=3;i<=N;i++)
    {
        while(Cnt>=2 && CrossProduct(P[St[Cnt-1]],P[St[Cnt]],P[i])>0) Cnt--;
        St[++Cnt]=i;
    }
    printf("%d\n",Cnt);
    for(i=Cnt;i;i--) printf("%lf %lf\n",P[St[i]].x,P[St[i]].y);
    return 0;
}