#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;
Point P[NMAX],St[NMAX];

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

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