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::*;
use std::str::FromStr;
use std::collections::HashMap;
use std::collections::BTreeSet;
use std::cmp;
use std::f64::consts;

fn main() {
    let n: i32 = read();
    let m: usize = read();

    let mut vec: Vec<(i32, i32)> = (0..m).map(|_| (read(), read())).collect();
    let mut map: HashMap<i32, Vec<(i32, i32)>> = HashMap::new();

    for &t in vec.iter() {
        if map.contains_key(&t.0) {
            let mut v: Vec<(i32,i32)> = map.get(&t.0).unwrap().clone();
            v.push(t);
            map.insert(t.0, v);
        } else {
            map.insert(t.0, vec![t]);
        }
    }

    let mut res: Vec<String> = Vec::new();
    for i in 0..m {
        res.push("".to_string());
    }

    for (key, mut value) in map {
        value.sort_by_key(|key| key.1);
        for (i, &e) in value.iter().enumerate() {
            let index: usize = vec.iter().position(|&r| r == e).unwrap();
            res[index] = format!("{:06}{:06}", key, i+1);
        }
    }

    for i in res {
        println!("{}", i);
    }
}

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("failed to read char") as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().expect("failed to parse token")
}