import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.*;
import java.math.BigInteger;
 
public class Main implements Runnable {
	
	static int mod = 1000000007;
	
    public static void main(String[] args) {
    	new Thread(null, new Main(), "", 1024 * 1024 * 1024).start();
    }
    
    public void run() {
       	PrintWriter out = new PrintWriter(System.out);
        FastScanner sc = new FastScanner();
        int n = sc.nextInt();
          
        ArrayList<Point> l = new ArrayList<>();
        for(int i=0;i<n;i++){
            double x = sc.nextDouble();
            double y = sc.nextDouble();
            Point p = new Point(x,y);
            l.add(p);
        }
        ConvexPolygon cp = ConvexPolygon.makeConvexPolygon(l);
          
        System.out.println(cp.pl.size());
          
        double miny = Double.POSITIVE_INFINITY;
        double minx = Double.POSITIVE_INFINITY;
        int sid = 0;
        for(int i=0;i<cp.pl.size();i++){
            double x = cp.pl.get(i).x;
            double y = cp.pl.get(i).y;
            if(y<miny){
                miny = y;
                minx = x;
                sid = i;
            }
            else if(y==miny){
                if(x<=minx){
                    minx = x;
                    sid = i;
                }
            }
        }
          
        for(int i=sid;i<cp.pl.size();i++){
            System.out.println((int)cp.pl.get(i).x +" "+(int)cp.pl.get(i).y);
        }
        for(int i=0;i<sid;i++){
            System.out.println((int)cp.pl.get(i).x +" "+(int)cp.pl.get(i).y);
        }
        out.flush();
    }

    
}

class Point implements Comparable<Point>{
	double x,y;
	static final double eps = 0.00000001;
	
	public Point(double a, double b){
		this.x = a;
		this.y = b;
	}
	
	//距離の2乗
	public double d2(Point b){
		return (x-b.x)*(x-b.x) + (y-b.y)*(y-b.y);
	}
	
	//通常のユークリッド距離
	public double dist(Point b){
		return Math.sqrt((x-b.x)*(x-b.x) + (y-b.y)*(y-b.y));
	}
	
	//p1へのベクトルからみてp2へのベクトルが反時計回りなら1、時計回りなら2
	//↑が同一直線状にあるとき、→p2が→p1と反対側なら3、→p2が→p1の延長線上なら4、→p2が→p1上にあれば5を返す
	int direction(Point p1, Point p2){
		
		if(p2.x == x && p2.y == y){
			return 5;
		}
		
		//外積の第三成分 = |→p1||→p2|sinθ
		double det = (p1.x -x)*(p2.y-y) - (p2.x -x)*(p1.y - y);
		
		if(det>eps){
			return 1;
		}
		else if(det<-eps){
			return 2;
		}
		else{	//同一直線状
			if((p1.x-x >0 == p2.x-x <0) && p1.x-x != 0){	//反対側
				return 3;
			}
			else if((p1.y-y >0 == p2.y-y <0) && p1.y-y != 0){	//反対側
				return 3;
			}
			else{
				double d10 = d2(p1);	//p1とp0の距離^2
				double d20 = d2(p2);	//p2とp0の距離^2
				if(d10 < d20){	//p2のほうが遠い
					return 4;
				}
				else{
					return 5;
				}
			}
		}
		
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		long temp;
		temp = Double.doubleToLongBits(x);
		result = prime * result + (int) (temp ^ (temp >>> 32));
		temp = Double.doubleToLongBits(y);
		result = prime * result + (int) (temp ^ (temp >>> 32));
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		Point other = (Point) obj;
		if (Double.doubleToLongBits(x) != Double.doubleToLongBits(other.x))
			return false;
		if (Double.doubleToLongBits(y) != Double.doubleToLongBits(other.y))
			return false;
		return true;
	}
	
	@Override
	public int compareTo(Point o){
		if(x!=o.x){
			return Double.compare(x,o.x);
		}
		return Double.compare(y, o.y);
	}
		
}

class Polygon {
	static final double eps = 0.00000001;
	ArrayList<Point> pl; //反時計周り
	
	public Polygon(ArrayList<Point> pol){
		this.pl = pol;
	}
	
	//面積を導出
	double area(){
		//|det|/2は作る三角形の面積に一致
		double ans = 0;
		
		for(int i=0;i<pl.size();i++){
			ans += det(pl.get(i), pl.get(next(i)));
		}
		
		return ans/2;
	}
	
	//pが多角形に含まれるなら2、pが辺上にあるなら1、pが外側にあるなら0を返す
	int contain(Point p){
		//pからx軸と平行・正方向の半直線を引き、奇数回交差すれば内部にある
		boolean isIn = false;
		for(int i=0;i<pl.size();i++){
			int upid = i;
			int downid = next(i);
			if(pl.get(i).y < pl.get(next(i)).y){
				upid = next(i);
				downid = i;
			}
			
			//ベクトルを便宜的に
			Point pup = new Point(pl.get(upid).x - p.x, pl.get(upid).y - p.y);	//p→p_i
			Point pdown = new Point(pl.get(downid).x - p.x, pl.get(downid).y - p.y); //p→p_next(i)
			
			double det = det(pup, pdown);
			if(pup.y > 0 && 0 >= pdown.y){	//2重カウントしないために不等号を>と>=にする
				if(det < 0){
					isIn = !isIn;
				}
			}
			
			//辺上判定
			if(Math.abs(det) < eps){	//p→p_iとp→p_next(i)が一直線上
				if(pup.x * pdown.x + pup.y * pdown.y <= 0){	//pからみて同方向でない
					return 1;
				}
			}
		}
		
		if(isIn){
			return 2;
		}
		else{
			return 0;
		}
	}
	
	//凸多角形か判定
	boolean isConvex(){
		//反時計回りに回り続けるなら凸
		for(int i=0;i<pl.size();i++){
			if(pl.get(next(i)).direction(pl.get(i),pl.get(next(next(i)))) == 1){
				return false;
			}
		}
		return true;
	}
	
	//反時計回りに1つ進んだ頂点のindex
	int next(int id){
		int size = pl.size();
		if(id<=size-2){
			return id+1;
		}
		else{
			return 0;
		}
	}
	//ベクトルのdet
	static double det(double x1, double y1, double x2, double y2){
		return x1*y2 - x2*y1;
	}
	static double det(Point p, Point q){
		return p.x*q.y - p.y*q.x;
	}
	
}

class ConvexPolygon extends Polygon{
	static final double allowableError = 0.00000001;
	
	//既に凸包で反時計回りのリストから作成
	public ConvexPolygon(ArrayList<Point> cp){
		super(cp);
	}
	
	//与えられた点のリストから凸包を作る
	//x最小の中でy最小の頂点から反時計回り
	static ConvexPolygon makeConvexPolygon(ArrayList<Point> l){
		Collections.sort(l);
		
		ArrayList<Point> up = new ArrayList<>(); //上側
		ArrayList<Point> down = new ArrayList<>(); //下側
		
		up.add(l.get(0));
		up.add(l.get(1));
		down.add(l.get(0));
		down.add(l.get(1));
		
		for(int i=2;i<l.size();i++){
			Point now = l.get(i);
			
			boolean con = true;
			while(con){
				Point p0 = down.get(down.size()-2);
				Point p1 = down.get(down.size()-1);
				int d = p0.direction(p1,now);
				if(d==2){ //p1が凹になる
					down.remove(down.size()-1);
					if(down.size()==1){
						con =false;
					}
				}
				else{
					con = false;
				}
			}
			
			down.add(now);
		}
		
		for(int i=2;i<l.size();i++){
			Point now = l.get(i);
			
			boolean con = true;
			while(con){
				Point p0 = up.get(up.size()-2);
				Point p1 = up.get(up.size()-1);
				int d = p0.direction(p1,now);
				if(d==1){ //p1が凹になる
					up.remove(up.size()-1);
					if(up.size()==1){
						con =false;
					}
				}
				else{
					con = false;
				}
			}
			
			up.add(now);
		}
		
		up.remove(0);
		up.remove(up.size()-1);
		Collections.reverse(up);
		down.addAll(up);
		
		return new ConvexPolygon(down);
	}
	
	//最遠頂点対間距離をキャリパー法で求める
	double diameter(){
		//まずx軸方向の最遠点対をとる
		double minx = Double.POSITIVE_INFINITY;
		int minxid = 0;
		double maxx = Double.NEGATIVE_INFINITY;
		int maxxid = 0;
		
		for(int i=0;i<pl.size();i++){
			double x = pl.get(i).x;
			if(x<minx){
				minx = x;
				minxid = i;
			}
			else if(x>maxx){
				maxx = x;
				maxxid = i;
			}
		}
		
		int pid = minxid;
		int qid = maxxid;
		
		double diamax = pl.get(pid).d2(pl.get(qid));
		
		boolean con = true;
		while(con){
			double x1 = pl.get(next(pid)).x - pl.get(pid).x;
			double y1 = pl.get(next(pid)).y - pl.get(pid).y;
			double x2 = pl.get(next(qid)).x - pl.get(qid).x;
			double y2 = pl.get(next(qid)).y - pl.get(qid).y;
			double det = det(x1,y1,x2,y2);
			if(det<0){
				pid = next(pid);
			}
			else{
				qid = next(qid);
			}
			diamax = Math.max(diamax,pl.get(pid).d2(pl.get(qid)));
			if(qid==next(minxid) || pid ==next(maxxid)){
				con = false;
			}
		}
		
		return Math.sqrt(diamax);
	}

}

class FastScanner {
	private final InputStream in = System.in;
	private final byte[] buffer = new byte[1024];
	private int ptr = 0;
	private int buflen = 0;
	private boolean hasNextByte() {
		if (ptr < buflen) {
			return true;
		} else {
			ptr = 0;
			try {
				buflen = in.read(buffer);
			} catch (IOException e) {
				e.printStackTrace();
			}
			if (buflen <= 0) {
				return false;
			}
		}
		return true;
	}
	private int readByte() {
		if (hasNextByte())
			return buffer[ptr++];
		else
			return -1;
	}
	private static boolean isPrintableChar(int c) {
		return 33 <= c && c <= 126;
	}
	public boolean hasNext() {
		while (hasNextByte() && !isPrintableChar(buffer[ptr]))
			ptr++;
		return hasNextByte();
	}
	public String next() {
		if (!hasNext())
			throw new NoSuchElementException();
		StringBuilder sb = new StringBuilder();
		int b = readByte();
		while (isPrintableChar(b)) {
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	public long nextLong() {
		if (!hasNext())
			throw new NoSuchElementException();
		long n = 0;
		boolean minus = false;
		int b = readByte();
		if (b == '-') {
			minus = true;
			b = readByte();
		}
		if (b < '0' || '9' < b) {
			throw new NumberFormatException();
		}
		while (true) {
			if ('0' <= b && b <= '9') {
				n *= 10;
				n += b - '0';
			} else if (b == -1 || !isPrintableChar(b)) {
				return minus ? -n : n;
			} else {
				throw new NumberFormatException();
			}
			b = readByte();
		}
	}
	public int nextInt() {
		long nl = nextLong();
		if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
			throw new NumberFormatException();
		return (int) nl;
	}
	public int[] nextintArray(int n){
		int[] a = new int[n];
		for(int i=0;i<n;i++){
			a[i] = nextInt();
		}
		return a;
	}
	public long[] nextlongArray(int n){
		long[] a = new long[n];
		for(int i=0;i<n;i++){
			a[i] = nextLong();
		}
		return a;
	}
	public Integer[] nextIntegerArray(int n){
		Integer[] a = new Integer[n];
		for(int i=0;i<n;i++){
			a[i] = nextInt();
		}
		return a;
	}
	public int[][] nextintMatrix(int h, int w){
		int[][] mat = new int[h][w];
		for(int i=0;i<h;i++){
			for(int j=0;j<w;j++){
				mat[i][j] = nextInt();
			}
		}
		return mat;
	}
	public double nextDouble() {
		return Double.parseDouble(next());
	}
}


Measured memory_bytes: 64680