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 (
	"bufio"
	"fmt"
	"os"
)

var sc = bufio.NewScanner(os.Stdin)
type City struct {
	Prefecture int64
	Year int64
	Pos int64
}

func main()  {
	var N, M int64
	fmt.Scan(&N)
	fmt.Scan(&M)
	cities := make([]City, M)
	prefectures := make(map[int64][]int64)

	for i := 0; int64(i) < M; i++ {
		fmt.Scan(&cities[i].Prefecture)
		fmt.Scan(&cities[i].Year)
		cities[i].Pos = 1
		if prefectures[cities[i].Prefecture] == nil {
			prefectures[cities[i].Prefecture] = []int64{}
		}
		for p := range prefectures[cities[i].Prefecture] {
			if cities[i].Year < cities[p].Year {
				cities[p].Pos++
			} else {
				cities[i].Pos++
			}
		}
		prefectures[cities[i].Prefecture] = append(prefectures[cities[i].Prefecture], int64(i))
	}
	for i := 0; int64(i) < M; i++ {
		fmt.Printf("%06d%06d\n", cities[i].Prefecture, cities[i].Pos)
	}
}