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 Go (1.6) (judge verdict: Accepted)

package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"strconv"
)

// const abcd = "abcdefghijklnmopqrstuvwxyz"
// const ABCD = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

// var dy = [...]int{1, 1, 0, -1, -1, -1, 0, 1}
// var dx = [...]int{0, 1, 1, 1, 0, -1, -1, -1}

// var dx = [...]int{0, 1, 0, -1}
// var dy = [...]int{1, 0, -1, 0}

// var inf int = 1e9
// var mod = 1000000007

// ---------------------------------------------------------
func main() {
	log.SetFlags(log.Lshortfile)
	next := newScanner()
	h := next.Int()
	w := next.Int()
	n := next.Int()
	a := make([]int, n)
	for i := 0; i < n; i++ {
		a[i] = next.Int()
	}
	mark := make([]int, h*w)
	k := 0
	for i, n := range a {
		i++
		for j := 0; j < n; j++ {
			// log.Println(k, h, w)
			mark[k] = i
			k++
		}
	}
	for i := 0; i < h; i++ {
		for j := 0; j < w; j++ {
			j1 := j
			if i%2 != 0 {
				j1 = w - j - 1
			}
			fmt.Print(mark[i*w+j1])
			if j != w-1 {
				fmt.Print(" ")
			}
		}
		fmt.Println("")
	}

}

// ---------------------------------------------------------

// Pair is liked C++ pair
type Pair struct {
	a, b int
}

// Pairs is sorted by []Pair struct
type Pairs []Pair

func (p Pairs) Len() int {
	return len(p)
}
func (p Pairs) Swap(i, j int) {
	p[i], p[j] = p[j], p[i]
}

func (p Pairs) Less(i, j int) bool {
	if p[i].a < p[j].a {
		return true
	} else if p[i].a == p[j].a {
		return p[i].b < p[j].b
	}
	return false
}

// -------------------------------
func in(c, a, z int) bool {
	return c >= a && c < z
}

func btoi(b bool) int {
	if b {
		return 1
	}
	return 0
}

func itob(a int) bool {
	if a == 0 {
		return false
	}
	return true
}

func max(a ...int) int {
	r := a[0]
	for i := 0; i < len(a); i++ {
		if r < a[i] {
			r = a[i]
		}
	}
	return r
}

func min(a ...int) int {
	r := a[0]
	for i := 0; i < len(a); i++ {
		if r > a[i] {
			r = a[i]
		}
	}
	return r
}

func minmax(a, b int) (int, int) {
	if a > b {
		return b, a
	}
	return a, b
}

func abs(a int) int {
	if a < 0 {
		return -a
	}
	return a
}

// ---------- buffered scanner -----------------------------------------
type scanner struct {
	r   *bufio.Reader
	buf []byte
	p   int
}

func newScanner() *scanner {
	rdr := bufio.NewReaderSize(os.Stdin, 10000)
	return &scanner{r: rdr}
}
func (s *scanner) next() string {
	s.pre()
	start := s.p
	for ; s.p < len(s.buf); s.p++ {
		if s.buf[s.p] == ' ' {
			break
		}
	}
	result := string(s.buf[start:s.p])
	s.p++
	return result
}
func (s *scanner) Line() string {
	s.pre()
	start := s.p
	s.p = len(s.buf)
	return string(s.buf[start:])
}
func (s *scanner) Int() int {
	v, _ := strconv.Atoi(s.next())
	return v
}
func (s *scanner) Int64() int64 {
	v, _ := strconv.ParseInt(s.next(), 10, 64)
	return v
}
func (s *scanner) pre() {
	if s.p >= len(s.buf) {
		s.readLine()
		s.p = 0
	}
}
func (s *scanner) readLine() {
	s.buf = make([]byte, 0)
	for {
		l, p, e := s.r.ReadLine()
		if e != nil {
			panic(e)
		}
		s.buf = append(s.buf, l...)
		if !p {
			break
		}
	}
}