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 kotlin.comparisons.*

fun main(args: Array<String>){
    val (N, M) = readLine()!!.split(" ").map { it.toInt() }
    val array = Array(M){ i -> readLine()!!.split(" ").map { it.toInt() }.let { CityInfo(it[0], it[1], "", i) }}
    array.sortWith(compareBy({ it.p }, { it.birth }))

    var i = 1
    var city = array[0].p
    for (a in array){
        if(city == a.p){
            a.num = add0(a.p) + add0(i)
        }else{
            i = 1
            a.num = add0(a.p) + add0(i)
        }
        city = a.p
        i++
    }
    array.sortBy { it.order }
    array.map { it.num }.joinToString("\n").let { println(it) }
}

class CityInfo(
    val p: Int,
    val birth: Int,
    var num: String = "",
    val order: Int
)

fun add0(i: Int): String{
    if(i.toString().length < 6){
        return "0".repeat(6 - i.toString().length) + i.toString()
    }else{
        return  i.toString()
    }
}