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>

struct city{
  int num,pref,year;
  char nums[13];
};

int comp1(const void *p1,const void *p2){
  struct city n1=*(const struct city *)p1;
  struct city n2=*(const struct city *)p2;

  return (n1.pref!=n2.pref) ? (n1.pref-n2.pref) : (n1.year-n2.year) ;
}

int comp2(const void *p1,const void *p2){
  struct city n1=*(const struct city *)p1;
  struct city n2=*(const struct city *)p2;

  return n1.num-n2.num;
}

int main(void){
  int N,M;
  int i,j,k=1;
  
  scanf("%d%d",&N,&M);
  struct city *cities;
  cities=(struct city *)calloc(M,sizeof(struct city));

  for(i=0;i<M;i++){
    cities[i].num=i;
    scanf("%d%d",&cities[i].pref,&cities[i].year);
  }

  qsort(cities,M,sizeof(struct city),comp1);
  
  int p;
  for(i=0,p=-1;i<M;i++){
    if(p!=cities[i].pref){
      p=cities[i].pref;
      k=1;
    }
    sprintf(cities[i].nums,"%06d%06d",cities[i].pref,k);
    ++k;
  }

  qsort(cities,M,sizeof(struct city),comp2);

  for(i=0;i<M;i++) printf("%s\n",cities[i].nums);
  
  free(cities);
  return 0;
}