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: Time Limit Exceeded)

package main

import (
	"bufio"
	"fmt"
	"os"
	"sort"
	"strconv"
	"strings"
)

type City struct {
	Ken   int
	Year  int
	Index int
	ID    string
}

func NewLine(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

type Citys []City

func (c Citys) Len() int           { return len(c) }
func (c Citys) Swap(i, j int)      { c[i], c[j] = c[j], c[i] }
func (c Citys) Less(i, j int) bool { return c[i].Year < c[j].Year }

func main() {
	sc := bufio.NewScanner(os.Stdin)
	line := NewLine(sc)
	words := strings.Fields(line)
	kenLength, _ := strconv.Atoi(words[0])
	cityLength, _ := strconv.Atoi(words[1])
	var citys []City
	citys = make([]City, 0, cityLength)
	for i := 0; i < cityLength; i++ {
		line = NewLine(sc)
		words = strings.Fields(line)
		ken, _ := strconv.Atoi(words[0])
		year, _ := strconv.Atoi(words[1])
		city := City{
			Ken:   ken,
			Year:  year,
			Index: i,
			ID:    "",
		}
		citys = append(citys, city)
	}

	for i := 0; i < kenLength; i++ {
		var citysOfKen = make([]City, 0, cityLength)
		for _, city := range citys {
			if i+1 == city.Ken {
				citysOfKen = append(citysOfKen, city)
			}
		}
		sort.Sort(Citys(citysOfKen))
		for i, city := range citysOfKen {
			city.ID = fmt.Sprintf("%06d%06d", city.Ken, i+1)
			citys[city.Index] = city
		}
	}
	for _, city := range citys {
		fmt.Println(city.ID)
	}
}