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: Time Limit Exceeded)

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

namespace test
{
    class Program
    {
        static void Main(string[] args)
        {
            var input = ReadArrayInt();
            var N = input[0];
            var M = input[1];
            var P = new int[M];
            var Y = new int[M];
            var pre = new Prefecture[N + 1];
            for (int i = 0; i <= N; i++) pre[i] = new Prefecture(i);
            for (int i = 0; i < M; i++)
            {
                input = ReadArrayInt();
                P[i] = input[0];
                Y[i] = input[1];
                pre[P[i]].CityAdd(Y[i]);
            }

            for (int i = 0; i < N + 1; i++) pre[i].CitySort();

            for (int i = 0; i < M; i++)
            {
                var ans = "";
                for (int j = 0; j < 6 - Digit(P[i]); j++) ans += "0";
                ans += P[i];
                var idx = pre[P[i]].BornNumber(Y[i]);
                for (int j = 0; j < 6 - Digit(idx); j++) ans += "0";
                ans += idx;
                Console.WriteLine(ans);
            }

            Console.WriteLine();
            Console.ReadLine();
        }

        static int Digit(int num)
        {
            return (num.ToString().Length);
        }

        static string Read() { return Console.ReadLine(); }
        static int ReadInt() { return int.Parse(Read()); }
        static long ReadLong() { return long.Parse(Read()); }
        static int[] ReadArrayInt() { return Read().Split(' ').Select(s => int.Parse(s)).ToArray(); }
        static long[] ReadArrayLong() { return Read().Split(' ').Select(s => long.Parse(s)).ToArray(); }
    }

    class Prefecture
    {
        public int number;
        public List<int> city;

        public Prefecture(int num)
        {
            number = num;
            city = new List<int>();
        }

        public void CityAdd(int num)
        {
            city.Add(num);            
        }

        public void CitySort()
        {
            if (city.Count > 1) city = city.OrderBy(i => i).ToList();
        }

        public int BornNumber(int num)
        {
            return city.IndexOf(num) + 1;
        }
    }
}