ConvexHullProblem

import java.util.*;
import java.io.*;
public class ConvexHullProblem {

    static int direction(Point a, Point b, Point c) {
        return (b.x - a.x) * (c.y - b.y) - (c.x - b.x) * (b.y - a.y);
    }

    public static void main(String[] args) throws IOException{
        readLine();
        int n = nextInt();

        Point[] points = new Point[n];

        for(int i = 0; i < n; i ++) {
            readLine();
            points[i] = new Point(nextInt(), nextInt());
        }
        Arrays.sort(points);

        Stack<Point> top = new Stack<Point>();

        for(int i = 0; i < n; i ++) {
            Point next = points[i];
            boolean cw = false;
            while(top.size() > 1 && ! cw) {
                Point b = top.pop();
                Point a = top.peek();
                if(direction(a, b, next) < 0) {
                    cw = true;
                    top.push(b);
                }
            }
            top.push(next);
        }

        Stack<Point> bottom = new Stack<Point>();
        for(int i = n - 1; i >= 0; i --) {
            Point next = points[i];
            boolean cw = false;
            while(bottom.size() > 1 && ! cw) {
                Point b = bottom.pop();
                Point a = bottom.peek();
                if(direction(a, b, next) < 0) {
                    cw = true;
                    bottom.push(b);
                }
            }
            bottom.push(next);
        }

        bottom.pop();
        bottom.remove(0);
        top.addAll(bottom);
        System.out.println(top);
    }
    static BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    static StringTokenizer st;
    static void readLine() throws IOException{
        st = new StringTokenizer(in.readLine());
    }
    static int nextInt() {
        return Integer.parseInt(st.nextToken());
    }
    static class Point implements Comparable<Point>{
        int x, y;
        Point(int x, int y){
            this.x = x;
            this.y = y;
        }
        @Override
        public int compareTo(Point o) {
            if(this.x == o.x) {
                return this.y - o.y;
            }
            return this.x - o.x;
        }
        public String toString(){
            return "(" + x + ", " + y + ")";
        }

    }
}