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)

from operator import itemgetter

def main():
    num_prefecture, num_city = list(map(int, input().rstrip().split()))
    prefecture_list = []
    for i in range(num_prefecture):
        prefecture_list.append([])
    #print(prefecture_list)
    id_list = []
    for idx_city in range(num_city):
        p_belong, y_born = list(map(int, input().rstrip().split()))
        p_belong -= 1 # 0から始まるようにする
        prefecture_list[p_belong].append([idx_city, y_born])
    
    #print(prefecture_list)
    # 各県のリスト内で, 市の誕生順にソートする
    for l in prefecture_list:
        l.sort(key = itemgetter(1))
    
    #print(prefecture_list)
    
    for idx_p, l in enumerate(prefecture_list):
        for x, [idx_city, y_born] in enumerate(l):
            id_first = '{0:06d}'.format(idx_p + 1)
            id_end = '{0:06d}'.format(x + 1)
            id_num = str(id_first) + str(id_end)
            id_list.append([idx_city, id_num])
    
    id_list.sort(key = itemgetter(0))
    
    for id_num in id_list:
        print(id_num[1])
    
if __name__ == '__main__':
    main()