#include <cstdio>
#include <algorithm>
#include <iomanip>
using namespace std;
#define MAXN 120005
int n,mnp=1,st[MAXN],nrst;
struct pc
{
    double x,y;
}v[MAXN];
double determinant(pc A, pc B, pc C)
{
    return (A.x-B.x)*(B.y-C.y) - (B.x-C.x)*(A.y-B.y);
}
bool cmp(pc A, pc B)
{
    return determinant(v[1],A,B)>0;
}
int main()
{
    int i,j;
    freopen("infasuratoare.in","r",stdin);
    freopen("infasuratoare.out","w",stdout);
    scanf("%d",&n);
    for(i=1; i<=n; i++)
        scanf("%lf%lf",&v[i].x,&v[i].y);


    for(i=2; i<=n; i++)
    {
        if(v[i].x<v[mnp].x || (v[i].x==v[mnp].x && v[i].y<v[mnp].y))
            mnp=i;
    }

    swap(v[mnp],v[1]);
    sort(v+2,v+n+1,cmp);

    for(i=1; i<=n; i++)
    {
        while(nrst>=2 && determinant(v[st[nrst-1]],v[st[nrst]], v[i]) <0)
            nrst--;

        st[++nrst]=i;
    }
    printf("%d\n",nrst);
    for(i=1; i<=nrst; i++)
        printf("%lf %lf\n",v[st[i]].x,v[st[i]].y);





}