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.Generic;
using System.Linq;

namespace ABC113_C
{
    class Program
    {
        static void Main(string[] args)
        {
            var NM = Console.ReadLine().Split().Select(int.Parse).ToArray();
            var N = NM[0];
            var M = NM[1];

            var P = new long[M];
            var Y = new long[M];
            var data = new List<Data>();
            
            for (int i = 0; i < M; i++)
            {
                var PY = Console.ReadLine().Split().Select(long.Parse).ToArray();
                var d = new Data()
                {
                    Id = i,
                    P = PY[0],
                    Y = PY[1]
                };

                data.Add(d);
            }

            data = (from d in data
                    orderby d.P, d.Y
                    select d).ToList();

            long tmpP = 0;
            var tmpcnt = 1;
            for (int i = 0; i < M; i++)
            {
                if (tmpP == data[i].P)
                {
                    tmpcnt++;
                }
                else
                {
                    tmpP = data[i].P;
                    tmpcnt = 1;
                }
                data[i].newY = tmpcnt;
            }

            data = data.OrderBy(x => x.Id).ToList();

            for (int i = 0; i < M; i++)
            {
                Console.WriteLine(data[i].P.ToString("000000") + data[i].newY.ToString("000000"));
            }
        }

        public class Data
        {
            public int Id { get; set; }
            public long P { get; set; }
            public long Y { get; set; }
            public int newY { get; set; }
        }
    }
}