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.Text;

namespace AtCoder
{
    class Program
    {
        private static string Read() { return Console.ReadLine(); }
        private static int ReadInt() { return int.Parse(Read()); }
        private static long ReadLong() { return long.Parse(Read()); }
        private static int[] ReadInts() { return Array.ConvertAll(Read().Split(), int.Parse); }
        private static long[] ReadLongs() { return Array.ConvertAll(Read().Split(), long.Parse); }

        class City
        {
            public readonly int n;
            public readonly int P;
            public readonly int Y;
            public City(int n, int[] V)
            {
                this.n = n;
                P = V[0];
                Y = V[1];
            }
        }
        static IEnumerable<string> Solve(City[] cities)
        {
            var dict = new Dictionary<int, List<City>>();
            foreach (var city in cities)
            {
                if (!dict.ContainsKey(city.P)) { dict[city.P] = new List<City>(); }
                dict[city.P].Add(city);
            }
            var ids = new List<Tuple<int, string>>();
            foreach (var list in dict.Values)
            {
                int i = 0;
                foreach (var city in list.OrderBy(city => city.Y))
                {
                    var id = string.Format("{0:D6}{1:D6}", city.P, ++i);
                    ids.Add(new Tuple<int, string>(city.n, id));
                }
            }
            return ids.OrderBy(id => id.Item1).Select(id => id.Item2);
        }
        static void Main(string[] args)
        {
            var V = ReadInts();
            int M = V[1];
            var cities = new City[M];
            for (int i = 0; i < M; ++i) { cities[i] = new City(i, ReadInts()); }
            foreach (var ans in Solve(cities)) { Console.WriteLine(ans); }
        }
    }
}