Problem:
Sorting Pairs

Write a program which print coordinates $(x_i, y_i)$ of given $n$ points on the plane by the following criteria.

first by $x$-coordinate

in case of a tie, by $y$-coordinate

Input

The input is given in the following format.

$n$
$x_0 \; y_0$
$x_1 \; y_1$
:
$x_{n-1} \; y_{n-1}$

In the first line, the number of points $n$ is given. In the following $n$ lines, coordinates of each point are given.

Output

Print coordinate of given points in order.

Constraints

$1 \leq n \leq 100,000$

$-1,000,000,000 \leq x_i, y_i \leq 1,000,000,000$

Sample Input 1

5
4 7
5 5
2 3
6 8
2 1

Sample Output 1

2 1
2 3
4 7
5 5
6 8

Solution in JAVA (judge verdict: Accepted)

import java.util.*;

class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        ArrayList<Pair> pairs = new ArrayList<>();
        for(int i = 0;i < n;i++){
            pairs.add(new Pair(sc.nextInt(),sc.nextInt()));
        }
        Collections.sort(pairs);
        Iterator<Pair> it = pairs.iterator();
        while(it.hasNext()){
            Pair a = it.next();
            a.print();
        }
    }

    static class Pair implements Comparable<Pair>{
        int x,y;
        Pair(int x,int y){
            this.x = x;
            this.y = y;
        }

        public int compareTo(Pair p){
            if(x < p.x) return -1;
            else if(x == p.x){
                if(y < p.y) return -1;
                else return 1;
            }
            else    return 1;
        }

        public void print(){
            System.out.println(x+" "+y);
        }
        
    }
}