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.Numerics;
using static System.Console;
using static System.Convert;
using static System.Math;

class Program
{
    class o
    {
        public int index;
        public int ye;
        public int city;
        public string number;

        public void GetN(string i)
        {
            var ind = city.ToString();
            var ze = "";
            for (var j = 0; j < 6 - ind.Length; j++) ze += "0";
            ze += ind;
            for (var j = 0; j < 6-i.Length; j++) ze += "0";
            ze += i;
            number = ze;
        }
    }

    static void Main(string[] args)
    {
        var input = ReadLine().Split(' ');
        var num = ToInt32(input[0]);
        var cit = ToInt32(input[1]);
        var os = new List<o>();
        for(var i = 0; i < cit; i++)
        {
            var inp = ReadLine().Split(' ');
            var s = new o();
            s.index = i;
            s.city = ToInt32(inp[0]);
            s.ye = ToInt32(inp[1]);
            os.Add(s);
        }
        os.Sort((a,b) => a.ye-b.ye);
        var dic = new Dictionary<int, int>();
        for(var i = 0; i < cit; i++)
        {
            var c = os[i].city;
            if (dic.ContainsKey(c))
            {
                os[i].GetN(dic[c].ToString());
                dic[c]++;
            }
            else
            {
                os[i].GetN("1");
                dic[c] = 2;
            }
        }
        os.Sort((a, b) => a.index - b.index);
        foreach(var n in os)
        {
            WriteLine(n.number);
        }
    }
}