#define REP(a,b) for(int a=0; a<(b); ++a)
#define FWD(a,b,c) for(int a=(b); a<(c); ++a)
#define FWDS(a,b,c,d) for(int a=(b); a<(c); a+=d)
#define BCK(a,b,c) for(int a=(b); a>(c); --a)
#define ALL(a) (a).begin(), (a).end()
#define SIZE(a) ((int)(a).size())
#define VAR(x) #x ": " << x << " "
#define FILL(x,y) memset(x,y,sizeof(x))
#define MIN(a,b) (((a)<(b))?(a):(b))
#define MAX(a,b) (((a)>(b))?(a):(b))
#define x first
#define y second
#define st first
#define nd second
#define pb push_back
#define l(n) (n<<1)
#define r(n) ((n<<1)+1)
#define f(n) (n>>1)
#define lsb(a) (a&-a)

#include<vector>
#include<algorithm>
#include<iomanip>

using namespace std;
#include<fstream>
ifstream cin("infasuratoare.in");
ofstream cout("infasuratoare.out");

const int NMAX = 120010;
const int INF = 0x3f3f3f3f;
const int dx[] = {0,0,-1,1}; //1,1,-1,1};
const int dy[] = {-1,1,0,0}; //1,-1,1,-1};

typedef long long LL;
typedef pair<int, int> PII;
typedef long double K;
typedef pair<K, K> PKK;
typedef vector<int> VI;

int n,m,k,t;

struct Point
{
	double x,y;
};

bool cmp(Point l, Point r)
{
	return (l.x<r.x || (l.x==r.x && l.y<r.y));
}

double orientation(Point a, Point b, Point c) 
{
	/*
		orientation < 0 then counter-clockwise
		orientation = 0 then collinear
		orientation > 0 then clockwise
	*/
	return (b.y-a.y)*(c.x-b.x)-(b.x-a.x)*(c.y-b.y);
}

Point P[NMAX];
Point H[NMAX<<1];

int main()
{
	ios_base::sync_with_stdio(true);
	cout<<setprecision(6)<<fixed;
	
	cin>>n;
	REP(i,n)
		cin>>P[i].x>>P[i].y;
		
	sort(P, P+n, cmp);
	
	int i;
	
	for(i=0, k=0; i<n; ++i)
	{
		while(k>=2 && orientation(H[k-2], H[k-1], P[i])<=0)
			k--;
		H[k++]=P[i];
	}
	
	for(i=n-2, t=k+1; i>=0; --i)
	{
		while(k>=t && orientation(H[k-2], H[k-1], P[i])<=0)
			k--;
		H[k++]=P[i];
	}
	
	/*
		H[i] hull of size k
	*/
	cout<<--k<<" \n";
	BCK(i,k-1,-1)
		cout<<1.00*H[i].x<<" "<<1.00*H[i].y<<"\n";
	

	return 0;
}