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 Python (3.4.3) (judge verdict: Accepted)

n, m = list(map(int, input().split()))
# [[preficture, year, num]...]
towns = [list(map(int, input().split())) + [i] for i in range(m)]
sort_towns = sorted(towns, key = lambda x : (x[0], x[1]))

prev_pref = 1
town_no = 1
for i in range(len(sort_towns)):
    pref = sort_towns[i][0]
    town = sort_towns[i][1]
    if not prev_pref == pref:
        town_no = 1
        prev_pref = pref
        sort_towns[i].append(town_no)
    sort_towns[i].append(town_no)
    town_no += 1
sort_towns = sorted(sort_towns, key=lambda x : x[2])
for i in range(len(sort_towns)):
    print(str(sort_towns[i][0]).zfill(6) + str(sort_towns[i][3]).zfill(6))