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 Ruby (2.3.3) (judge verdict: Wrong Answer)

def inputInts
    gets.chomp.split(" ").map(&:to_i)
end

def getId(p, x)
    format('%06d', p) + format('%06d', x)
end

@N, @M = inputInts
@pres = {}
@cities = {}

(1..@N).each do |i|
    @pres[i] = []
end

(1..@M).each do |i|
    p, y = inputInts
    @pres[p] << i
    @cities[i] = [p, y]
end

# sort cities by founded year
(1..@N).each do |i|
    if @pres[i].length > 1
        @pres[i].sort {|a, b| @cities[a][1] <=> @cities[b][1] }
    end
end

# add indexes to cities
(1..@N).each do |i|
    if @pres[i].length > 0
        @pres[i].each_with_index do |city, i|
            @cities[city] << i + 1
        end
    end
end

(1..@M).each do |i|
    city = @cities[i]
    puts getId(city[0], city[2])
end