Problem:
Score: 300 points

Problem Statement

In Republic of Atcoder, there are N prefectures, and a total of M cities that belong to those prefectures.

City i is established in year Y_i and belongs to Prefecture P_i.

You can assume that there are no multiple cities that are established in the same year.

It is decided to allocate a 12-digit ID number to each city.

If City i is the x-th established city among the cities that belong to Prefecture i, the first six digits of the ID number of City i is P_i, and the last six digits of the ID number is x.

Here, if P_i or x (or both) has less than six digits, zeros are added to the left until it has six digits.

Find the ID numbers for all the cities.

Note that there can be a prefecture with no cities.

Constraints

1 \leq N \leq 10^5

1 \leq M \leq 10^5

1 \leq P_i \leq N

1 \leq Y_i \leq 10^9

Y_i are all different.

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N M
P_1 Y_1
:
P_M Y_M

Output

Print the ID numbers for all the cities, in ascending order of indices (City 1, City 2, ...).

Sample Input 1

2 3
1 32
2 63
1 12

Sample Output 1

000001000002
000002000001
000001000001

As City 1 is the second established city among the cities that belong to Prefecture 1, its ID number is 000001000002.

As City 2 is the first established city among the cities that belong to Prefecture 2, its ID number is 000002000001.

As City 3 is the first established city among the cities that belong to Prefecture 1, its ID number is 000001000001.

Sample Input 2

2 3
2 55
2 77
2 99

Sample Output 2

000002000001
000002000002
000002000003

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.io.*;
import java.util.*;

public class Main {

  public static class City {
    int P;
    int Y;
    int index;

    public City(int P, int Y, int index) {
      this.P = P;
      this.Y = Y;
      this.index = index;
    }
  }

  public static void main(String[] args) throws Exception {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    String[] input = br.readLine().split(" ");
    int N = Integer.parseInt(input[0]);
    int M = Integer.parseInt(input[1]);
    int[] P = new int[M];
    int[] Y = new int[M];
    long[] ID = new long[M];
    City[] city = new City[M];
    for (int i = 0; i < M; i++) {
      input = br.readLine().split(" ");
      P[i] = Integer.parseInt(input[0]);
      Y[i] = Integer.parseInt(input[1]);
      city[i] = new City(P[i], Y[i], i);
    }
    Arrays.sort(city, (a, b) -> a.P == b.P ? a.Y - b.Y : a.P - b.P);
    int before = city[0].P;
    int order = 1;
    for (int i = 0; i < M; i++) {
      int now = city[i].P;
      if (before != now) {
        before = now;
        order = 1;
      }
      ID[city[i].index] = order;
      order++;
    }
    for (int i = 0; i < M; i++) {
      System.out.println(String.format("%06d", P[i]) + String.format("%06d", ID[i]));
    }
  }
}