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 Rust (1.15.1) (judge verdict: Accepted)

use std::io::Read;

fn main() {
    let mut buf = String::new();

    std::io::stdin().read_to_string(&mut buf).unwrap();

    let mut iter = buf.split_whitespace();
    let n: usize = iter.next().unwrap().parse().unwrap();
    let m: usize = iter.next().unwrap().parse().unwrap();
    let mut p = vec![0; m];
    let mut y = vec![0; m];
    for i in 0..m {
        p[i] = iter.next().unwrap().parse().unwrap();
        y[i] = iter.next().unwrap().parse().unwrap();
    }
    let mut permutation: Vec<usize> = (0..m).collect();
    permutation.sort_by(|i,j| {
        if p[*i] != p[*j] {
            return p[*i].cmp(&p[*j]);
        }
        y[*i].cmp(&y[*j])
    });
    let mut pre_id = -1;
    let mut sub_id = 1;
    let mut ans: Vec<String> = vec![String::new(); m];
    for i in permutation {
        if p[i] == pre_id {
            sub_id += 1;
        }else {
            sub_id = 1;
        }
        ans[i] = format!("{:0>6}{:0>6}", p[i], sub_id);
        pre_id = p[i];
    }
    for line in ans {
        println!("{}", line);
    }
}