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)

private fun readInts() = readLine()!!.split(" ").map { it.toInt() }

fun main(args: Array<String>) {
    val (N, M) = readInts()
    val pys = (0 until M).map { readInts() }

    val numbers = pys.mapIndexed { index, py -> CityNumber(py[0], py[1], index) }

    val inputtedRankMap = mutableMapOf<Int, Int>()
    numbers
            .sortedBy { cityNumber -> cityNumber.pref * 10000 + cityNumber.year }
            .asSequence()
            .map { cityNumber ->
                cityNumber.copy(formatNumber = "%06d".format(cityNumber.pref) + "%06d".format(inputtedRankMap.getOrElse(cityNumber.pref, { 1 }).apply {
                    inputtedRankMap[cityNumber.pref] = this + 1
                }))
            }
            .sortedBy { cityNumber -> cityNumber.inputRank }
            .forEach { cityNumber ->
                println(cityNumber.formatNumber)
            }
}

private data class CityNumber(
        val pref: Int,
        internal val year: Int,
        val inputRank: Int,
        var formatNumber: String = ""
)