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 Kotlin (1.0.0) (judge verdict: Accepted)

import java.util.*

fun main(args : Array<String>) {
    println(inOutExec(null))
}

fun inOutExec(scanner: Scanner?): String {
    val (numOfPref, numOfCity) = readLine()!!.split(" ").map { it.toInt() }

    val citiesIn = mutableListOf<Pair<Int, Int>>()
    repeat(numOfCity) {
        val (pref, year) = readLine()!!.split(" ").map { it.toInt() }
        citiesIn.add(Pair(pref, year))
    }

    val cityCodeMap = citiesIn
            .asSequence()
            .groupByTo(mutableMapOf()) { it.first }
            .flatMap { entry -> entry.value
                        .asSequence()
                        .sortedBy { info -> info.second }
                        .mapIndexed { index, pair ->
                            pair to "%06d%06d".format(pair.first, index + 1) }
                    .toList()
            } // Pair<Pair<Int, Int>, String>
            .toMap()

    return citiesIn.joinToString(separator = "\n", postfix = "\n") { cityCodeMap[it]!! }
}