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: Runtime Error)

import java.io.PrintWriter

@JvmField val _writer = PrintWriter(System.out, false)
fun main(args: Array<String>) { _writer.solve(); _writer.flush() }
fun PrintWriter.solve() {
    val (n, m) = readLine()!!.split(' ').map { it.toInt() }

    val data = mutableMapOf<Int, MutableList<Int>>()
    val inp = arrayOfNulls<Pair<Int,Int>>(m)
    repeat(m) {
        val (p, y) = readLine()!!.split(' ').map { it.toInt() }
        inp[it] = p to y
        if(data[p] == null) data[p] = mutableListOf()
        data[p]!!.add(y)
    }

    val sorted = mutableMapOf<Int, MutableMap<Int,Int>>()
    repeat(n) { ken ->
        val shiList = data[ken]
        if (shiList != null) {
            val shiSorted = mutableMapOf<Int, Int>()
            var cnt = 1
            shiList.sortedBy { it }.forEach {
                shiSorted[it] = cnt
                cnt++
            }
            sorted[ken] = shiSorted
        }
    }

    inp.forEach {
        println("%06d".format(it!!.first) + "%06d".format(sorted[it.first]!![it.second]) )
    }
}