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::io::prelude::*;

fn input<T>() -> T
where
    T: std::str::FromStr,
{
    let stdin = std::io::stdin();
    let token: String = stdin
        .lock()
        .bytes()
        .map(|c| c.unwrap() as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().unwrap()
}

fn main() {
    let h: usize = input();
    let w: usize = input();
    let n: usize = input();
    let a: Vec<i64> = (0..n).map(|_| input()).collect();

    let mut c = vec![vec![0; w]; h];
    let mut i = 0;
    let mut j = 0;
    for x in 0..n {
        let mut cnt = 0;
        while cnt < a[x] {
            c[i][j] = x + 1;
            cnt += 1;
            j += 1;
            if j == w {
                j = 0;
                i += 1;
            }
        }
    }

    for i in 0..h {
        if i % 2 > 0 {
            c[i].reverse();
        }
    }

    let out = std::io::stdout();
    let mut buf = std::io::BufWriter::new(out.lock());
    for i in 0..h {
        write!(buf, "{}", c[i][0]).unwrap();
        for j in 1..w {
            write!(buf, " {}", c[i][j]).unwrap();
        }
        writeln!(buf, "").unwrap();
    }
}