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 C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#include <stdlib.h>
#define MAX_N 100000

typedef struct {
  int n;
  char id[13];
  int P;
  int Y;
} st_city;

int city_sort(const void*a, const void*b) {
  int x = ((st_city*)a)->P - ((st_city*)b)->P;
  if(x != 0)
    return x;
  return (((st_city*)a)->Y - ((st_city*)b)->Y);
}

int n_sort(const void*a, const void*b) {
  return (((st_city*)a)->n - ((st_city*)b)->n);
}

int main(void) {
  int N, M;
  scanf("%d %d", &N, &M);

  st_city city[MAX_N];
  for(int i = 0; i < M; i++) {
    city[i].n = i;
    scanf("%d %d", &city[i].P, &city[i].Y);
  }
  qsort(city, M, sizeof(st_city), city_sort);

  int n = 1;
  int prevP = -1;
  for(int i = 0; i < M; i++) {
    if(prevP != city[i].P)
      n = 1;
    sprintf(city[i].id, "%06d%06d", city[i].P, n++);
    prevP = city[i].P;
  }

  qsort(city, M, sizeof(st_city), n_sort);
  for(int i = 0; i < M; i++) {
    printf("%s\n", city[i].id);
  }

  return 0;
}