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.Linq;

class Program
{
    static void Main(string[] args) {
        int[] s = Console.ReadLine().Split().Select(int.Parse).ToArray();
        int n = s[0];
        int m = s[1];
        int[][] l = new int[m][];
        for (int i = 0; i < m; i ++) {
            l[i] = new int[4];
            int[] a = Console.ReadLine().Split().Select(int.Parse).ToArray();
            l[i][0] = i;
            l[i][1] = a[0];
            l[i][2] = a[1];
        }
        Array.Sort(l, (a, b) => a[2] - b[2]);
        int[] c = new int[n];
        for(int i = 0; i < m; i ++) {
            c[l[i][1]-1] ++;
            l[i][3] = c[l[i][1]-1];
        }
        Array.Sort(l, (a, b) => a[0] - b[0]);
        for(int i = 0; i < m; i ++) {
            Console.WriteLine(String.Format("{0:D6}", l[i][1]) + String.Format("{0:D6}", l[i][3]));
        }
    }
}