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 Scala (2.11.7) (judge verdict: Accepted)

import scala.annotation.tailrec

object Main {
  def main(args: Array[String]): Unit = {
    val sc = new java.util.Scanner(System.in)
    val h, w = sc.nextInt
    val n = sc.nextInt
    val as = Vector.fill(n)(sc.nextInt)

    val rows = split(go(1, as, Vector[Vector[Int]]()).flatten, w)
    val ans = reverseOdd(rows)

    ans.foreach{ a =>
      a.foreach { b =>
        printf("%s ", b)
      }
      println()
    }

  }

  @tailrec
  def go(i: Int, seq: Seq[Int], result: Seq[Seq[Int]]): Seq[Seq[Int]] = {
    if (seq.length == 0) result
    else go(i+1, seq.tail, result :+ Seq.fill(seq.head)(i))
  }

  def split(seq: Seq[Int], n: Int): Seq[Seq[Int]] = {
    def go(s: Seq[Int], result: Seq[Seq[Int]]): Seq[Seq[Int]] = {
      if (s.length == 0) result
      else go(s.drop(n), result :+ s.dropRight(s.length - n))
    }
    go(seq, Seq[Seq[Int]]())
  }

  def reverseOdd(seq: Seq[Seq[Int]]): Seq[Seq[Int]] = {
    def go(i: Int, s: Seq[Seq[Int]], result: Seq[Seq[Int]]): Seq[Seq[Int]] = {
      if (s.length == 0) result
      else if (i % 2 == 0) go(i+1, s.tail, result :+ s.head)
      else go(i+1, s.tail, result :+ s.head.reverse)
    }
    go(0, seq, Seq[Seq[Int]]())
  }
}