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>
using namespace std;
using ll = long long;


void solve(long long H, long long W, long long N, std::vector<long long> a)
{
    vector<vector<ll>> ans(H, vector<ll>(W));
    ll color_no = 1;
    ll color_count = a[0];
    for (ll i = 0; i < H; ++i) {
        for (ll j = 0; j < W; ++ j) {
            auto jj = ((i % 2) == 0 ? j : W - j - 1);
            ans[i][jj] = color_no;
            color_count--;
            if (color_count == 0) {
                color_no++;
                color_count = a[color_no - 1];
            }
        }
    }

    for (auto&& a : ans){
        copy(begin(a), end(a), ostream_iterator<ll>(cout, " "));
        cout << "\n";
    }
}

// Generated by 1.1.6 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
// clang-format off
int main(){
    long long H;
    scanf("%lld",&H);
    long long W;
    scanf("%lld",&W);
    long long N;
    scanf("%lld",&N);
    std::vector<long long> a(N);
    for(int i = 0 ; i < N ; i++){
        scanf("%lld",&a[i]);
    }
    cin.tie(nullptr);
    cout.tie(nullptr);
	ios_base::sync_with_stdio(false);
    solve(H, W, N, std::move(a));
    return 0;
}