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>

typedef struct pair{
  int x,y,z;
}point;

int compare(const void *a,const void *b){
  return (*(point*)a).z > (*(point*)b).z;
}

int compare_int(const void *a,const void *b){
  if((*(point*)a).x == (*(point*)b).x){
    return (*(point*)a).y > (*(point*)b).y;
  }
  return (*(point*)a).x > (*(point*)b).x;
}

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

  point arr[M];
  for(int i = 0;i < M;i++){
    scanf("%d %d",&arr[i].x,&arr[i].y);
    arr[i].z = i;
  }

  qsort(arr,M,sizeof(point),compare_int);

  int p = arr[0].x;
  int cnt = 0;
  for(int i = 0;i < M;i++){
    if(arr[i].x != p){
      p = arr[i].x;
      cnt = 0;
    }
    arr[i].y = ++cnt;
  }

  qsort(arr,M,sizeof(point),compare);

  for(int i = 0;i < M;i++){
    printf("%06d%06d\n",arr[i].x,arr[i].y);
  }

  return 0;
}