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)

package main

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

type Tuple struct {
	value int
	index int
}

func main() {
	sc := NewScanner()
	N, M := sc.NextInt(), sc.NextInt()

	Q := make([]SortInterFace, N+1)
	for i := 0; i < N+1; i++ {
		Q[i] = make(SortInterFace, 0)
	}

	for i := 0; i < M; i++ {
		p, y := sc.NextInt(), sc.NextInt()
		Q[p] = append(Q[p], Tuple{y, i})
	}

	ans := make([]string, M)

	for i := 1; i <= N; i++ {
		sort.Sort(Q[i])
		for j := 0; j < len(Q[i]); j++ {
			ans[Q[i][j].index] = fmt.Sprintf("%06d%06d", i, j+1)
		}
	}
	for i := 0; i < M; i++ {
		fmt.Println(ans[i])
	}

}

type SortInterFace []Tuple

func (s SortInterFace) Len() int {
	return len(s)
}
func (s SortInterFace) Less(i, j int) bool {
	return s[i].value < s[j].value
}
func (s SortInterFace) Swap(i, j int) {
	s[i], s[j] = s[j], s[i]
}

type Scanner struct {
	r   *bufio.Reader
	buf []byte
	p   int
}

func NewScanner() *Scanner {
	rdr := bufio.NewReaderSize(os.Stdin, 1000)
	return &Scanner{r: rdr}
}
func (s *Scanner) Next() string {
	s.pre()
	start := s.p
	for ; s.p < len(s.buf); s.p++ {
		if s.buf[s.p] == ' ' {
			break
		}
	}
	result := string(s.buf[start:s.p])
	s.p++
	return result
}
func (s *Scanner) NextLine() string {
	s.pre()
	start := s.p
	s.p = len(s.buf)
	return string(s.buf[start:])
}
func (s *Scanner) NextInt() int {
	v, _ := strconv.Atoi(s.Next())
	return v
}
func (s *Scanner) NextInt64() int64 {
	v, _ := strconv.ParseInt(s.Next(), 10, 64)
	return v
}

func (s *Scanner) NextIntArray() []int {
	s.pre()
	start := s.p
	result := []int{}
	for ; s.p < len(s.buf)+1; s.p++ {
		if s.p == len(s.buf) || s.buf[s.p] == ' ' {
			v, _ := strconv.ParseInt(string(s.buf[start:s.p]), 10, 0)
			result = append(result, int(v))
			start = s.p + 1
		}
	}

	return result
}
func (s *Scanner) NextInt64Array() []int64 {
	s.pre()
	start := s.p
	result := []int64{}
	for ; s.p < len(s.buf)+1; s.p++ {
		if s.p == len(s.buf) || s.buf[s.p] == ' ' {
			v, _ := strconv.ParseInt(string(s.buf[start:s.p]), 10, 64)
			result = append(result, v)
			start = s.p + 1
		}
	}
	return result
}

func (s *Scanner) NextMap() map[int]bool {
	s.pre()
	start := s.p
	mp := map[int]bool{}
	for ; s.p < len(s.buf); s.p++ {
		if s.buf[s.p] == ' ' {
			v, _ := strconv.Atoi(string(s.buf[start:s.p]))
			mp[v] = true
			start = s.p + 1
		}
	}
	v, _ := strconv.Atoi(string(s.buf[start:s.p]))
	mp[v] = true

	return mp
}

func (s *Scanner) pre() {
	if s.p >= len(s.buf) {
		s.readLine()
		s.p = 0
	}
}
func (s *Scanner) readLine() {
	s.buf = make([]byte, 0)
	for {
		l, p, e := s.r.ReadLine()
		if e != nil {
			panic(e)
		}
		s.buf = append(s.buf, l...)
		if !p {
			break
		}
	}
}