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: Wrong Answer)

fun main(args: Array<String>) {
    val (n, m) = readLine()!!.split(" ").map(String::toInt)
    val vs = mutableListOf<Pair<Int, Int>>()
    val hs = hashMapOf<Int, MutableList<Int>>()

    for (i in 0..m-1) {
        val (p, y) = readLine()!!.split(" ").map(String::toInt)
        vs.add(Pair(p, y))
        if (hs[p] == null) {
            hs[p] = mutableListOf()
        }
        hs[p]!!.add(y)
    }

    for (j in hs.keys) {
        hs[j]!!.sorted()
    }

    for (k in 0..vs.size-1) {
        val p = vs[k]
        val rank = hs[p.first]!!.indexOf(p.second) + 1
        val ranks = rank.toString()

        println("${p.second.toString().padStart(6, '0')}${ranks.padStart(6,'0' )}")
    }
}