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: Time Limit Exceeded)

import java.util.ArrayList

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

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

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

    val citiesMap = mutableMapOf<Int, MutableSet<Pair<Int, Int>>>()
    citiesIn.sortedBy { it.second }
            .forEach {
                if (it.first !in citiesMap) citiesMap[it.first] = mutableSetOf()
                citiesMap[it.first]!!.add(it)
            }

    val sb = StringBuilder()
    for (city in citiesIn) {
        sb.append(city.first.toString().padStart(6, '0'))
                .append((citiesMap[city.first]!!.indexOf(city) + 1).toString().padStart(6, '0'))
                .append("\n")
    }
    return sb.toString()
}