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# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;

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

            var array = new(int P, int C) [m];
            var dic = new Dictionary < (int P, int C),
                string > ();

            for (var i = 0; i < m; i++)
            {
                var py = Console.ReadLine().Split(' ').Select(num => int.Parse(num)).ToArray();
                var tpl = (py[0], py[1]);
                array[i] = tpl;
            }
            var tmpArray = array.OrderBy(tpl => tpl.P).ThenBy(tpl => tpl.C).ToArray();

            var pCnt = 0;
            var pCode = "";
            var cCodeMemo = new Dictionary<int, string>();
            for (var i = 0; i < m; i++)
            {
                var tpl = tmpArray[i];
                if (i == 0 || tmpArray[i - 1].P != tpl.P)
                {
                    pCnt = 1;
                    pCode = GetCode(tpl.P);
                }
                else { pCnt++; }

                if (cCodeMemo.TryGetValue(pCnt, out var code))
                {
                    dic.Add(tpl, pCode + code);
                }
                else
                {
                    var cCode = GetCode(pCnt);
                    dic.Add(tpl, pCode + cCode);
                }
            }

            foreach (var tpl in array)
            {
                Console.WriteLine(dic[tpl]);
            }

            string GetCode(int num)
            {
                var d = (int) Math.Log10(num) + 1;
                return new string('0', 6 - d) + num.ToString();
            }
        }
    }
}