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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;

//Submission #3535255 - AtCoder Beginner Contest 113 | AtCoder 
// https://abc113.contest.atcoder.jp/submissions/3535255
public class Program_ABC113_C_kuuso1
{
    public static void Main()
    {
        int N, M;
        int[] P, Y;

        var d = ria();
        N = d[0];
        M = d[1];
        P = new int[M];
        Y = new int[M];
        for (int i = 0; i < M; i++)
        {
            d = ria();
            P[i] = d[0];
            Y[i] = d[1];
        }

        var di = new Dictionary<int, List<int[]>>();
        for (int i = 0; i < M; i++)
        {
            if (!di.ContainsKey(P[i]))
            {
                di.Add(P[i], new List<int[]>());
            }

            di[P[i]].Add(new[] { i, Y[i] });
        }

        String[] ans = new String[M];
        foreach (var pr in di.Keys)
        {
            var l = di[pr].ToList();
            l.Sort((p, q) => p[1].CompareTo(q[1]));
            for (int i = 0; i < l.Count; i++)
            {
                ans[l[i][0]] = String.Format("{0:D06}{1:D06}", pr, i + 1);
            }
        }

        Console.WriteLine(String.Join("\r\n", ans));
    }  //main

    static int[] ria(char sep = ' ') { return Array.ConvertAll(Console.ReadLine().Split(sep), e => int.Parse(e)); }

}