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;
using System.IO;
using System.Text;
using static System.Console;
using static System.Math;

namespace CP
{
    class Atria
    {
        static void Main(string[] args)
        {
            long[] nm = ReadLine().Split(' ').Select(long.Parse).ToArray();
            long n = nm[0];
            long m = nm[1];
            var ls = new List<hoge>();
            for (long i = 0; i < m; i++)
            {
                long[] s = ReadLine().Split(' ').Select(long.Parse).ToArray();
                long p = s[0];
                long y = s[1];
                ls.Add(new hoge() { id = p, year = y, index = i });
            }
            ls = ls.OrderBy(x => x.id).ThenBy(y => y.year).ToList();

            var ans = new SortedDictionary<long,string>();
            long cnt = 1;long rem = ls[0].id; 
            for (int i = 0; i < m; i++)
            {
                long p = ls[i].id;
                long index = ls[i].index;
                if (rem != p) { cnt = 1; rem = p; }
                ans.Add(index,string.Format("{0:000000}{1:000000}",p,cnt));
                cnt++;
            }
            foreach (var item in ans)
            {
                WriteLine(item.Value);
            }
        }
    }

    class hoge
    {
        public long id { get; set; }
        public long year { get; set; }
        public long index { get; set; }
    }
}