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)

#[allow(unused_imports)]
use template::buf_scan::*;
#[allow(unused_imports)]
use template::*;

#[allow(dead_code)]
#[macro_use]
pub mod macros {
    #[macro_export]
    macro_rules! debug {
        ($($a:expr),*) => {{
            use ::std::io::Write;
            writeln!(&mut ::std::io::stderr(), concat!($(stringify!($a), " = {:?}, "),*), $($a),*).unwrap();
        }}
    }

    #[macro_export]
    macro_rules! input {
        (source = $s:expr, $($r:tt)*) => {
            let mut scanner = $crate::template::buf_scan::BufScanner::new($s.as_bytes());
            input_inner!{scanner, $($r)*}
        };
        ($($r:tt)*) => {
            let stdin = ::std::io::stdin();
            let mut scanner = $crate::template::buf_scan::BufScanner::new(stdin.lock());
            input_inner!{scanner, $($r)*}
        };
    }

    macro_rules! input_inner {
        ($scanner:expr) => {};
        ($scanner:expr, ) => {};
        ($scanner:ident, $var:ident : $t:tt $($r:tt)*) => {
            let $var = read_value!($scanner, $t);
            input_inner!{$scanner $($r)*}
        };
        ($scanner:ident, mut $var:ident : $t:tt $($r:tt)*) => {
            let mut $var = read_value!($scanner, $t);
            input_inner!{$scanner $($r)*}
        };
    }

    macro_rules! read_value {
        ($scanner:ident, ( $($t:tt),* )) => {
            ( $(read_value!($scanner, $t)),* )
        };
        ($scanner:ident, [ $t:tt ; $len:expr ]) => {
            (0..$len).map(|_| read_value!($scanner, $t)).collect::<Vec<_>>()
        };
        ($scanner:ident, chars) => {
            read_value!($scanner, String).chars().collect::<Vec<char>>()
        };
        ($scanner:ident, usize1) => {
            read_value!($scanner, usize) - 1usize
        };
        ($scanner:ident, $t:ty) => {
            ($scanner).next::<$t>()
        };
    }
}

fn main() {
    input! {
        n: usize,
        m: usize,
        cities: [(usize1, usize); m],
    }

    let cities: Vec<(usize, usize)> = cities;

    let mut years_per_prefecture: Vec<Vec<usize>> = vec![Vec::new(); n];
    for &(p, y) in cities.as_slice() {
        years_per_prefecture[p].push(y);
    }
    for mut years in years_per_prefecture.as_mut_slice() {
        years.sort();
    }
    for &(p, y) in cities.as_slice() {
        match years_per_prefecture[p].binary_search(&y) {
            Ok(idx) => {
                println!("{:06}{:06}", p+1, idx+1)
            },
            Err(_) => {
                panic!()
            }
        }
    }
}

#[allow(dead_code)]
pub mod template {
    pub mod buf_scan {
        pub struct BufScanner<R: ::std::io::BufRead> {
            br: R,
            buf: Vec<u8>,
            pos: usize,
        }

        impl<R: ::std::io::BufRead> BufScanner<R> {
            pub fn new(br: R) -> Self {
                BufScanner {
                    br: br,
                    buf: Vec::new(),
                    pos: 0usize,
                }
            }
            fn fill_line(&mut self) {
                self.buf.clear();
                self.pos = 0;
                self.br
                    .read_until(b'\n', &mut self.buf)
                    .expect("Read a line");
                if let Some(&b'\n') = self.buf.last() {
                    self.buf.pop();
                    if let Some(&b'\r') = self.buf.last() {
                        self.buf.pop();
                    }
                }
            }
            fn skip_space(&mut self) {
                loop {
                    for i in self.pos..self.buf.len() {
                        if self.buf[i] != b' ' {
                            self.pos = i;
                            return;
                        }
                    }
                    self.fill_line();
                }
            }
            pub fn read_token(&mut self) -> &str {
                self.skip_space();
                let start = self.pos;
                while self.pos < self.buf.len() && self.buf[self.pos] != b' ' {
                    self.pos += 1;
                }
                let ret = unsafe { ::std::str::from_utf8_unchecked(&self.buf[start..self.pos]) };
                self.pos += 1; // skip the last space (or len() + 1 which is fine)
                return ret;
            }
            pub fn next<T: ::std::str::FromStr>(&mut self) -> T {
                self.read_token().parse::<T>().ok().expect("Parse")
            }
        }
    }
}