import java.io.*;
import java.util.*;
public class jobs {
public static void main(String[] args) throws IOException {
Reader in = new Reader();
PrintWriter out = new PrintWriter(System.out);
int n = in.nextInt();
int d = in.nextInt();
int m = in.nextInt();
Pair[] arr = new Pair[m];
for(int i = 0; i < m; i++) {
arr[i] = new Pair(i + 1, in.nextInt());
}
Arrays.sort(arr, Comparator.comparingInt(x -> x.day));
// for(Pair pairs : arr) {
// out.println(pairs.request + " " + pairs.day);
// }
int low = 0;
int high = m + 1;
int answer = 0;
List<List<Integer>> ansList = null;
while (low <= high) {
// out.println(low + " " + high);
int middle = (low + high) / 2;
List<List<Integer>> list = new ArrayList<>();
if (m / middle > n) {
low = middle + 1;
continue;
}
boolean works = true;
for (int i = 0; i < m; i += middle) {
list.add(new ArrayList<>());
for (int j = i; j < i + middle; j++) {
list.get(i / middle).add(arr[j].request);
if (arr[j].day >= i / middle + d + 1) { //if day surpasses delay, lower range and continue
works = false;
}
}
}
if(works) {
answer = middle;
ansList = list;
break;
} else {
high = middle - 1;
}
}
out.println(answer);
for(List<Integer> list : ansList) {
for(Integer integer : list) {
out.print(integer + " ");
}
out.print(0);
out.println();
}
if(ansList.size() < n) {
for(int i = 0; i < n - ansList.size(); i++) {
out.println(0);
}
}
// out.println(Arrays.toString(arr));
in.close();
out.close();
}
static class Pair {
int request, day;
Pair(int request, int day) {
this.request = request;
this.day = day;
}
}
static class Reader {
final private int BUFFER_SIZE = 1 << 16;
private DataInputStream din;
private byte[] buffer;
private int bufferPointer, bytesRead;
public Reader() {
din = new DataInputStream(System.in);
buffer = new byte[BUFFER_SIZE];
bufferPointer = bytesRead = 0;
}
public Reader(String file_name) throws IOException {
din = new DataInputStream(
new FileInputStream(file_name));
buffer = new byte[BUFFER_SIZE];
bufferPointer = bytesRead = 0;
}
public String readLine() throws IOException {
byte[] buf = new byte[64];
int cnt = 0, c;
while ((c = read()) != -1) {
if (c == '\n') {
if (cnt != 0) {
break;
} else {
continue;
}
}
buf[cnt++] = (byte) c;
}
return new String(buf, 0, cnt);
}
public int nextInt() throws IOException {
int ret = 0;
byte c = read();
while (c <= ' ') {
c = read();
}
boolean neg = (c == '-');
if (neg)
c = read();
do {
ret = ret * 10 + c - '0';
} while ((c = read()) >= '0' && c <= '9');
if (neg)
return -ret;
return ret;
}
public long nextLong() throws IOException {
long ret = 0;
byte c = read();
while (c <= ' ')
c = read();
boolean neg = (c == '-');
if (neg)
c = read();
do {
ret = ret * 10 + c - '0';
} while ((c = read()) >= '0' && c <= '9');
if (neg)
return -ret;
return ret;
}
public double nextDouble() throws IOException {
double ret = 0, div = 1;
byte c = read();
while (c <= ' ')
c = read();
boolean neg = (c == '-');
if (neg)
c = read();
do {
ret = ret * 10 + c - '0';
} while ((c = read()) >= '0' && c <= '9');
if (c == '.') {
while ((c = read()) >= '0' && c <= '9') {
ret += (c - '0') / (div *= 10);
}
}
if (neg)
return -ret;
return ret;
}
private void fillBuffer() throws IOException {
bytesRead = din.read(buffer, bufferPointer = 0,
BUFFER_SIZE);
if (bytesRead == -1)
buffer[0] = -1;
}
private byte read() throws IOException {
if (bufferPointer == bytesRead)
fillBuffer();
return buffer[bufferPointer++];
}
public void close() throws IOException {
if (din == null)
return;
din.close();
}
}
}
