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.Text;
using System.Linq;
using System;

public class P
{
    public int id { get; set; }
    public int city { get; set; }
    public int no { get; set; }
    public int y { get; set; }
}

public class Hello
{
    public static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var n = int.Parse(line[0]);
        var m = int.Parse(line[1]);
        var ps = new P[m];
        for (int i = 0; i < m; i++)
        {
            line = Console.ReadLine().Trim().Split(' ');
            var p = int.Parse(line[0]);
            var y = int.Parse(line[1]);
            ps[i] = new P { id = i, city = p, y = y };
        }
        var ps2 = ps.OrderBy(x => x.city).ThenBy(x => x.y).ToArray();
        var pre = ps2[0].city;
        ps2[0].no = 1;
        var pp = 1;
        for (int i = 1; i < m; i++)
        {
            if (pre == ps2[i].city) { ps2[i].no = ++pp; }
            else { ps2[i].no = 1; pp = 1; pre = ps2[i].city; }
        }
        var sb = new StringBuilder();
        foreach (var x in ps2.OrderBy(y => y.id).ToArray())
        {
            sb.Append(string.Format("{0:000000}", x.city));
            sb.Append(string.Format("{0:000000}\n", x.no));
        }
        Console.Write(sb);
    }
}