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::*;
use std::str::FromStr;

#[allow(dead_code)]
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")
}

fn calc(v: usize, n: usize, used: usize) -> usize {
    if v > n {
        return 0;
    }
    let mut ret = 0;
    if used == 7 {
        ret = 1;
    }
    for i in 0..3 {
        let nused = used | (1 << i);
        let t = [7, 5, 3][i];
        let nv = v * 10 + t;
        ret += calc(nv, n, nused);
    }
    return ret;
}

fn main() {
    let n = read::<usize>();
    let m = read::<usize>();
    let mut city = vec![(0, 0, 0); m];
    for i in 0..m {
        city[i].1 = read::<usize>() - 1;
        city[i].0 = read::<usize>();
        city[i].2 = i;
    }
    city.sort();
    let mut cnts = vec![0; n];
    let mut anss = vec![(0, "".to_string()); m];
    for i in 0..m {
        let c = city[i].1;
        cnts[c] += 1;
        anss[i].0 = city[i].2;
        anss[i].1 = format!("{:06}{:06}", c + 1, cnts[c]);
    }
    anss.sort();
    for i in 0..m {
        println!("{}", anss[i].1);
    }
}