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;

class City
{
    public int i, p, y, b;

    public City(int i, int p, int y)
    {
        this.i = i;
        this.p = p;
        this.y = y;
    }
}

class Program
{
    static void Main(string[] args)
    {
        var nm = Console.ReadLine().Split(' ');
        var n = int.Parse(nm[0]);
        var m = int.Parse(nm[1]);

        var cities = new City[m];
        for (int i = 0; i < m; i++)
        {
            var py = Console.ReadLine().Split(' ');
            cities[i] = new City(i, int.Parse(py[0]), int.Parse(py[1]));
        }

        Array.Sort(cities, (a, b) => a.p == b.p ? a.y - b.y : a.p - b.p);

        cities[0].b = 1;
        for (int i = 1; i < m; i++)
        {
            if (cities[i - 1].p == cities[i].p)
            {
                cities[i].b = cities[i - 1].b + 1;
            }
            else
            {
                cities[i].b = 1;
            }
        }

        Array.Sort(cities, (a, b) => a.i - b.i);

        for (int i = 0; i < m; i++)
        {
            Console.WriteLine("{0:D6}{1:D6}", cities[i].p, cities[i].b);
        }
    }
}