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)

fun main(args: Array<String>) {
    val (n, m) = readInputLine().split(" ").map { it.toInt() }
    // (pref, year)
    val cities = mutableListOf<Pair<Int, Int>>()
    // (pref, years)
    val map = mutableMapOf<Int, MutableList<Int>>()
    
    for (i in 1..m) {
        val (p, y) = readInputLine().split(" ").map { it.toInt() }
        cities.add(Pair(p, y))
        
        val prefInfo = map.get(p) ?: mutableListOf<Int>()
        prefInfo.add(y)
        map.put(p, prefInfo)
    }
    
    // 各県の年数をソート
    map.forEach { it.value.sort() }
    
    for (city in cities) {
        val prefInfo = map.get(city.first)!!
        println(city.first.toString().padStart(6, '0') + (prefInfo.indexOf(city.second) + 1).toString().padStart(6, '0'))
    }
}

fun readInputLine(): String {
    return readLine()!!
}