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 (1.42.0) (judge verdict: Accepted)

use proconio::input;
use std::collections::{HashMap, BTreeMap};
use std::fmt::Write;

fn main() {
    input! {
        _n: usize,
        m: usize,
        py: [(usize, usize); m],
    }

    let mut nums = vec![None; m];

    let mut prefectures = HashMap::new();
    
    for (i, (p, y)) in py.into_iter().enumerate() {
        prefectures.entry(p).or_insert_with(|| BTreeMap::new()).insert(y, i);
    }

    for (prefecture, cities) in prefectures {
        for (i, (_year, order)) in cities.into_iter().enumerate() {
            nums[order] = Some(format!("{:06}{:06}", prefecture, i+1));
        }
    }

    let mut ans = String::new();
    for num in nums {
        if let Some(num) = num {
            writeln!(ans, "{}", num).unwrap();
        } else {
            unreachable!();
        }
    }
    print!("{}", ans);
}