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: Accepted)

// go:generate go-assets-builder > assets.go

package main

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

type input struct {
	pos     int
	year    int
	sortNum int
}

type inputs []input

func (input inputs) Len() int {
	return len(input)
}
func (input inputs) Swap(i, j int) {
	input[i], input[j] = input[j], input[i]
}
func (input inputs) Less(i, j int) bool {
	return input[i].year < input[j].year
}
func (input inputs) remove(i int) inputs {
	if i >= len(input) {
		return input
	}
	return append(input[:i], input[i+1:]...)
}

func main() {
	sc.Split(bufio.ScanWords)
	// sc.Split(bufio.ScanLines)
	n := readInt()
	m := readInt()
	numMap := make(map[int][]int)
	yearArr := make([]int, 0, m)
	for i := 0; i < m; i++ {
		cityNum := readInt()
		year := readInt()
		numMap[cityNum] = append(numMap[cityNum], year)
		yearArr = append(yearArr, year)
	}

	yearMap := make(map[int]string)
	for i := 1; i <= n; i++ {
		arr := numMap[i]
		sort.Ints(arr)
		for j, v := range arr {
			yearMap[v] = fmt.Sprintf("%06d%06d", i, j+1)
		}
	}
	for _, year := range yearArr {
		fmt.Println(yearMap[year])
	}
}

//便利関数群
var sc = bufio.NewScanner(os.Stdin)

func read() string {
	sc.Scan()
	return sc.Text()
}

func readInt() int {
	i, _ := strconv.Atoi(read())
	return i
}

func max(x, y int) int {
	if x > y {
		return x
	} else {
		return y
	}
}

func min(x, y int) int {
	if x < y {
		return x
	} else {
		return y
	}
}

func abs(x, y int) int {
	if x-y > 0 {
		return x - y
	}
	return -(x - y)
}

type XY struct {
	x, y int
}

type Points []XY

func (p Points) Len() int {
	return len(p)
}
func (p Points) Swap(i, j int) {
	p[i], p[j] = p[j], p[i]
}
func (p Points) Less(i, j int) bool {
	return p[i].x < p[j].x
}
func (p Points) remove(i int) Points {
	if i >= len(p) {
		return p
	}
	return append(p[:i], p[i+1:]...)
}