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: Wrong Answer)

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

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("filed 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 main() {
    let n: usize = read();
    let m: usize = read();
    let mut p: Vec<usize> = Vec::new();
    let mut y: Vec<usize> = Vec::new();
    for _ in 0..m {
        p.push(read());
        y.push(read());
    }
    let mut v = vec![Vec::new(); n + 1];
    for i in 0..m {
        v[p[i]].push(y[i]);
    }
    for i in 0..n {
        v[i].sort();
        v[i].dedup();
    }

    for i in 0..m {
        let x = p[i];
        print!("{:06}", x);

        let id = lower_bound(&v[x], y[i]);
        print!("{:06}", id + 1);
        println!("");
    }
}

fn lower_bound(v: &Vec<usize>, x: usize) -> usize {
    let mut l = 0;
    let mut r = v.len() - 1;
    while l < r {
        let mid = (l + r) / 2;
        if x <= v[mid] {
            r = mid;
        } else {
            l = mid + 1;
        }
    }
    l
}