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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
#include <cassert>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;

const long long MOD = 1000000007;
const long long INF = 1LL << 60;
const int INT_INF = 1000000000;

int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};

int main()
{
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int H, W;
  cin >> H >> W;
  int N;
  cin >> N;
  vector<int> a(N);
  for (auto &ai : a)
    cin >> ai;
  vector<vector<int>> grid(H, vector<int>(W));

  int now = 0;
  int rem = a[now];

  for (int i = 0; i < H; i++)
  {
    if (i % 2 == 0)
    {
      for (int j = 0; j < W; j++)
      {
        grid[i][j] = now + 1;
        rem--;
        if (rem == 0)
        {
          now++;
          rem = a[now];
        }
      }
    }
    else
    {
      for (int j = W - 1; j >= 0; j--)
      {
        grid[i][j] = now + 1;
        rem--;
        if (rem == 0)
        {
          now++;
          rem = a[now];
        }
      }
    }
  }
  for (int i = 0; i < H; i++)
  {
    for (int j = 0; j < W; j++)
    {
      cout << grid[i][j] << " ";
    }
    cout << endl;
  }
  return 0;
}