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 (Clang 3.8.0) (judge verdict: Accepted)

#include <stdio.h>
#include <stdlib.h>

typedef struct {
    int num;
    int p;
    long long y;
    char id[13];
} city_t;

int compare_num(const void *a, const void *b)
{
    return ((city_t*)a)->num - ((city_t*)b)->num;
}

int compare_p(const void *a, const void *b)
{
    return ((city_t*)a)->p - ((city_t*)b)->p;
}

int compare_y(const void *a, const void *b)
{
    if (((city_t*)a)->y - ((city_t*)b)->y < 0)
        return -1;
    if (((city_t*)a)->y - ((city_t*)b)->y > 0)
        return 1;
    return 0;
}

int main (void)
{
    int N, M;
    city_t city[(int)1e5];
    int i, start = 0, end = 0, x = 1;

    scanf("%d %d", &N, &M);

    for (i = 0; i < M; i++) {
        city[i].num = i;
        scanf("%d %lld", &city[i].p, &city[i].y);
    }

    qsort(city, M, sizeof(city_t), compare_p);

    // for (i = 0; i < M; i++) {
    //     printf("%d %lld %s\n", city[i].p, city[i].y, city[i].id);
    // }

    while (start < M) {
        for (end = start; end < M; end++) {
            // printf("%d==%d?\n", city[end].p, city[end + 1].p);
            if (city[end].p != city[end + 1].p) break;
        }
        // printf("%d->%d\n", start, end);
        qsort(&city[start], end - start + 1, sizeof(city_t), compare_y);
        start = end + 1;
    }

    for (i = 0; i < M; i++) {
        sprintf((char*)&city[i].id, "%06d%06d", city[i].p, x++);
        if (city[i].p != city[i + 1].p) x = 1;
    }

    // for (i = 0; i < M; i++) {
    //     printf("%d %lld %s\n", city[i].p, city[i].y, city[i].id);
    // }

    qsort(city, M, sizeof(city_t), compare_num);

    for (i = 0; i < M; i++) {
        puts(city[i].id);
    }
}