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: Wrong Answer)

import numpy as np
from operator import itemgetter

N, M = input().split()
N, M = int(N), int(M)
C = [input().split() for i in range(M)]

for i, c in enumerate(C):
  C[i] = [int(c[0]), int(c[1])]
  C[i].append(i)

C_sorted = sorted(C, key = lambda x: (x[0], x[1]))

counter = 1
current = 1

for c in C_sorted:
  if current < c[0]:
    counter = 1
  pref = str(c[0])
  num = str(counter)
  number = ''
  for i in range(6 - len(pref)):
    number += '0'
  number += pref
  for i in range(6 - len(num)):
    number += '0'
  number += num

  c.append(number)
  counter += 1
  current = c[0]

print(C_sorted)

C_reversed = sorted(C_sorted, key = lambda x: x[2])

for c in C_reversed:
  print(c[3])