#include <cstdio>
#include <algorithm>

using namespace std;

#define maxn 120005

struct point
{
    double x,y;
};

int n;
point v[maxn];
point stack[maxn];
int lv;
void read()
{
    freopen("infasuratoare.in","r",stdin);

    int i;

    scanf("%d\n",&n);

    for(i=1;i<=n;++i)
        scanf("%lf %lf",&v[i].x,&v[i].y);
}

inline double cross(const point &a,const point &b,const point &c)
{
    return (b.x-a.x) * (c.y-a.y) - (c.x-a.x) * (b.y-a.y);
}

struct comp
{
    inline bool operator ()(const point &a,const point &b) const
    {
        return cross(v[1],a,b)<0;
    }
};

void pre()
{
    int fnd = 1,i;
    for(i=2;i<=n;++i)
        if(v[i].x < v[fnd].x || (v[i].x == v[fnd].x && v[i].y < v[fnd].y))
            fnd = i;
    swap(v[1],v[fnd]);
    sort(v+2,v+n+1,comp());
}

void solve()
{
    int i;
    stack[1] = v[1];
    stack[2] = v[2];
    lv = 2;
    for(i=3;i<=n;++i)
    {
        while(lv >= 2 && cross(stack[lv-1],stack[lv],v[i]) > 0)
            --lv;
        stack[++lv]=v[i];
    }
}

void write()
{
    freopen("infasuratoare.out","w",stdout);
    int i;
    printf("%d\n",lv);
    for(i=lv;i;--i)
        printf("%.9lf %.9lf\n",stack[i].x,stack[i].y);
}

int main()
{
    read();
    pre();
    solve();
    write();
    return 0;
}