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;
class Program
{
	static void Main(string[] args)
	{
		string[] str = Console.ReadLine().Split();
		int N = int.Parse(str[0]);
		int M = int.Parse(str[1]);
		int[][] B = new int[M][];
		for(var i=0;i<M;i++){
			B[i] = new int[3];
			string[] str2 = Console.ReadLine().Split();
			B[i][0] = int.Parse(str2[0]);
			B[i][1] = int.Parse(str2[1]);
			B[i][2] = i;
		}
		Array.Sort(B,(x,y)=>x[1] - y[1]);
		int[,] C = new int[M,2];
		int[] D = new int[N];
		for(var i=0;i<M;i++){
			C[B[i][2],0] = B[i][0];
			C[B[i][2],1] = D[B[i][0]-1]+1;
			D[B[i][0]-1] += 1;
		}
		string[] E = new string[M];
		for(var i=0;i<M;i++){
			string a1 = "000000"+C[i,0].ToString();
			a1 = a1.Substring(a1.Length-6,6);
			string a2 = "000000"+C[i,1].ToString();
			a2 = a2.Substring(a2.Length-6,6);
			E[i] = a1+a2;
		}		
		for(var i=0;i<M;i++){
			Console.WriteLine(E[i]);
		}
	}
}