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: Time Limit Exceeded)

use std::io::{self, Read};

fn main() {
    let mut buffer = String::new();
    io::stdin().read_to_string(&mut buffer).unwrap();
    let mut iter = buffer.split_whitespace();

    let n: usize = iter.next().unwrap().parse().unwrap();
    let m: usize = iter.next().unwrap().parse().unwrap();

    let mut prefectures = Vec::with_capacity(m);
    for _ in 0..m {
        let p: usize = iter.next().unwrap().parse().unwrap();
        let y: usize = iter.next().unwrap().parse().unwrap();
        prefectures.push((p, y));
    }

    let mut prefectures_cities = Vec::with_capacity(n);

    for i in 1..(n + 1) {
        let mut cities = Vec::new();
        for p in &prefectures {
            if p.0 == i {
                cities.push(p.1);
            }
        }
        cities.sort();
        prefectures_cities.push(cities);
    }

    for p in prefectures {
        println!(
            "{:06}{:06}",
            p.0,
            prefectures_cities[p.0 - 1].binary_search(&p.1).unwrap() + 1
        );
    }
}