Problem:
Score : 400 points

Problem Statement

We have a grid with H rows and W columns of squares.
Snuke is painting these squares in colors 1, 2, ..., N.
Here, the following conditions should be satisfied:

For each i (1 ≤ i ≤ N), there are exactly a_i squares painted in Color i. Here, a_1 + a_2 + ... + a_N = H W.

For each i (1 ≤ i ≤ N), the squares painted in Color i are 4-connected. That is, every square painted in Color i can be reached from every square painted in Color i by repeatedly traveling to a horizontally or vertically adjacent square painted in Color i.

Find a way to paint the squares so that the conditions are satisfied.
It can be shown that a solution always exists.

Constraints

1 ≤ H, W ≤ 100

1 ≤ N ≤ H W

a_i ≥ 1

a_1 + a_2 + ... + a_N = H W

Input

Input is given from Standard Input in the following format:

H W
N
a_1 a_2 ... a_N

Output

Print one way to paint the squares that satisfies the conditions.
Output in the following format:

c_{1 1} ... c_{1 W}
:
c_{H 1} ... c_{H W}

Here, c_{i j} is the color of the square at the i-th row from the top and j-th column from the left.

Sample Input 1

2 2
3
2 1 1

Sample Output 1

1 1
2 3

Below is an example of an invalid solution:

1 2
3 1

This is because the squares painted in Color 1 are not 4-connected.

Sample Input 2

3 5
5
1 2 3 4 5

Sample Output 2

1 4 4 4 3
2 5 4 5 3
2 5 5 5 3

Sample Input 3

1 1
1
1

Sample Output 3

1

Solution in Rust (1.15.1) (judge verdict: Accepted)

use std::error::Error;
use std::io::{self, BufReader};
use std::io::prelude::*;
use std::str::{self, FromStr};

fn exec() {
    let mut sc = Scanner::new(io::stdin());
    let (h, w, n): (usize, usize, usize) = (sc.ne(), sc.ne(), sc.ne());
    let a: Vec<usize> = (0..n).map(|_| sc.ne()).collect();
    let mut v = Vec::new();
    for i in 0..n {
        for _ in 0..a[i] {
            v.push(i + 1);
        }
    }
    for i in 0..h {
        let ans = if i % 2 == 0 {
            v[i * w..(i + 1) * w].to_owned()
        } else {
            let mut tmp = v[i * w..(i + 1) * w].to_owned();
            tmp.reverse();
            tmp
        };
        for j in 0..w {
            print!("{} ", ans[j]);
        }
        println!("");
    }
}


fn main() {
    const STACK: usize = 16 * 1024 * 1024;
    let _ = std::thread::Builder::new()
        .stack_size(STACK)
        .spawn(|| { exec(); })
        .unwrap()
        .join()
        .unwrap();
}

#[allow(dead_code)]
pub struct Scanner<R> {
    bufread: BufReader<R>,
    id: usize,
    buf: Vec<u8>,
}
impl<R: Read> Scanner<R> {
    pub fn new(resource: R) -> Scanner<R> {
        Scanner {
            bufread: BufReader::new(resource),
            id: 0,
            buf: Vec::new(),
        }
    }
    fn next_line(&mut self) -> Option<String> {
        let mut res = String::new();
        match self.bufread.read_line(&mut res) {
            Ok(0) => None,
            Ok(_) => Some(res),
            Err(why) => panic!("error in read_line: {}", why.description()),
        }
    }
    pub fn next<T: FromStr>(&mut self) -> Option<T> {
        while self.buf.is_empty() {
            self.buf = match self.next_line() {
                Some(r) => {
                    self.id = 0;
                    r.trim().as_bytes().to_owned()
                }
                None => return None,
            };
        }
        let l = self.id;
        assert_ne!(self.buf[l], b' ');
        let n = self.buf.len();
        let mut r = l;
        while r < n && self.buf[r] != b' ' {
            r += 1;
        }
        let res = match str::from_utf8(&self.buf[l..r]).ok().unwrap().parse::<T>() {
            Ok(s) => Some(s),
            Err(_) => {
                panic!(
                    "parse error, {:?}",
                    String::from_utf8(self.buf[l..r].to_owned())
                )
            }
        };
        while r < n && self.buf[r] == b' ' {
            r += 1;
        }
        if r == n {
            self.buf.clear();
        } else {
            self.id = r;
        }
        res
    }
    pub fn ne<T: FromStr>(&mut self) -> T {
        self.next::<T>().unwrap()
    }
}