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"
        "sort"
        "strconv"
        "strings"
)

////////////////////////////////////////
///        templates                 ///
////////////////////////////////////////

var sc = bufio.NewScanner(os.Stdin)

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

var rdr = bufio.NewReaderSize(os.Stdin, 1000000)

func readBigLine() string {
        buf := make([]byte, 0, 1000000)
        for {
                l, p, e := rdr.ReadLine()
                if e != nil {
                        panic(e)
                }
                buf = append(buf, l...)
                if !p {
                        break
                }
        }
        return string(buf)
}

func strSprit(str string) []string {
        cols := strings.Split(str, " ")
        return cols
}

func parseInt(str string) int {
        n, _ := strconv.Atoi(str)
        return n
}

func intSprit(str string) []int {
        strs := strSprit(str)
        cols := make([]int, len(strs))
        for i, v := range strs {
                cols[i] = parseInt(v)
        }
        return cols
}

func bitCount(n uint) int {

        x := uint64(n)

        const m = 1<<64 - 1
        const m0 = 0x5555555555555555
        const m1 = 0x3333333333333333
        const m2 = 0x0f0f0f0f0f0f0f0f

        x = x>>1&(m0&m) + x&(m0&m)
        x = x>>2&(m1&m) + x&(m1&m)
        x = (x>>4 + x) & (m2 & m)
        x += x >> 8
        x += x >> 16
        x += x >> 32

        return int(x) & (1<<7 - 1)
}

func bitExist(n, i int) bool {
        return ((n >> uint(i)) & 1) == 1
}

////////////////////////////////////////
///        end templates             ///
////////////////////////////////////////
type Pair struct {
        p, y int
}

func main() {
        line := nextLine()

        spl := strSprit(line)
        N := parseInt(spl[0])
        M := parseInt(spl[1])

        indexes := make(map[Pair]int, M)
        years := make([][]int, N+1)
        for i := 0; i <= N; i++ {
                years[i] = []int{}
        }

        for i := 1; i <= M; i++ {
                s := intSprit(nextLine())
                years[s[0]] = append(years[s[0]], s[1])
                p := Pair{s[0], s[1]}
                indexes[p] = i
        }

        for i := 0; i < N; i++ {
                sort.Ints(years[i])
        }

        ans := make([]string, M+1)

        for i := 1; i <= N; i++ {
                y := years[i]
                for idx, val := range y {
                        tp := Pair{i, val}
                        ai := indexes[tp]
                        ans[ai] = fmt.Sprintf("%06d%06d", i, idx+1)
                }
        }
        for i := 1; i <= M; i++ {
                fmt.Println(ans[i])
        }

}