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 Go (1.6) (judge verdict: Wrong Answer)

package main

import (
	"fmt"
	"sort"
)

func main() {
	var n, m int
	fmt.Scan(&n, &m)

	ids := make(Ids, m)
	num := make([]int, n)
	dict := map[Id]int{}
	for i := range ids {
		fmt.Scan(&ids[i].p, &ids[i].y)
		a := &Id{ids[i].p, ids[i].y}
		dict[*a] = 0
	}
	ids2 := make(Ids, m)
	copy(ids2, ids)
	sort.Sort(ids)

	for i:=0;i<m;i++{
		num[ids[i].p-1]++
		a := &Id{ids[i].p, ids[i].y}
		dict[*a] = num[ids[i].p-1]
	}
	for i:=0;i<m;i++ {
		a := &Id{ids2[i].p, ids2[i].y}
		fmt.Printf("%04d%04d\n", ids2[i].p, dict[*a])
	}
}


type Id struct {
	p int
	y int
}

type Ids []Id

func (a Ids) Len() int {
	return len(a)
}

func (a Ids) Swap(i, j int)  {
	a[i], a[j] = a[j], a[i]
}

func (a Ids) Less(i, j int) bool {
	if a[i].p < a[j].p {
		return true
	} else if a[i].p == a[j].p {
		if a[i].y < a[j].y {
			return true
		}
	}
	return false
}