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.Linq;
using System.Collections.Generic;
namespace abc_113_c
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] NM = Console.ReadLine().Split(' ');
            int N = int.Parse(NM[0]);
            int M = int.Parse(NM[1]);
            var D = new List<List<int>>();
            for (int i = 0; i < M; i++)
            {
                string[] PY = Console.ReadLine().Split(' ');
                int p = int.Parse(PY[0]);
                int y = int.Parse(PY[1]);                
                D.Add(new List<int>{p, y, i});
            }
            var SD = D.OrderBy(x => x[1]);
            var P = new Dictionary<int, int>();
            int[] C = new int[M];
            foreach (List<int> sd in SD )
            {
                int pref = sd[0];
                int year = sd[1];
                int city = sd[2];
                if (!P.ContainsKey(pref)) P[pref] = 0;
                P[pref] += 1;
                C[city] = P[pref];
            }
            for (int i = 0; i < M; i++)
            {
                Console.WriteLine("{0:000000}{1:000000}", D[i][0], C[i]);
            }
        }
    }
}