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;
using System.Threading.Tasks;

namespace ConsoleApp86 {
    class Program {
        static void Main(string[] args) {
            var st = Console.ReadLine().Split().Select(int.Parse).ToArray();
            int N = st[0];
            int M = st[1];

            var P = new int[M];
            var Y = new int[M];
            var index = new int[M];

            for (int i = 0; i < M; i++) {
                var x = Console.ReadLine().Split().Select(int.Parse).ToArray();
                P[i] = x[0];
                Y[i] = x[1];
                index[i] = i;
            }

            var cityList = new List<Tuple<int, int>>[N];

            //初期化
            for (int i = 0; i < N; i++) {
                cityList[i] = new List<Tuple<int, int>>();
            }

            //数字を格納していく
            for (int i = 0; i < M; i++) {
                cityList[P[i] - 1].Add(new Tuple<int, int>(index[i], Y[i]));
            }

            //ソート
            for (int i = 0; i < N; i++) {
                cityList[i].Sort((p, q) => p.Item2.CompareTo(q.Item2));
            }

            var ans = new int[M];
            int counter;

            //答えに数値を当てはめていく
            for (int i = 0; i < N; i++) {
                counter = 1;
                for (int j = 0; j < cityList[i].Count(); j++) {
                    ans[cityList[i][j].Item1] = counter;
                    counter++;
                }
            }

            for (int i = 0; i < M; i++) {
                Console.WriteLine(String.Format("{0:D6}", P[i]) + String.Format("{0:D6}", ans[i]));
            }
        }
    }
}