import java.io.*;
import java.util.*;
public class jobs {
static ArrayList<ArrayList<Integer>> schedule = new ArrayList<>();
static int N, D, M;
static int[][] jobs;
public static void main(String... args) throws IOException {
// BufferedReader reader = new BufferedReader(new FileReader("input.in"));
BufferedReader reader = new BufferedReader(new InputStreamReader(new DataInputStream(System.in)));
PrintWriter writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
StringTokenizer st = new StringTokenizer(reader.readLine());
N = Integer.parseInt(st.nextToken());
D = Integer.parseInt(st.nextToken());
M = Integer.parseInt(st.nextToken());
st = new StringTokenizer(reader.readLine());
jobs = new int[M][];
for (int i = 0; i < M; i++) {
jobs[i] = new int[] {i + 1, Integer.parseInt(st.nextToken())};
}
Arrays.sort(jobs, Comparator.comparingInt(j -> j[1]));
// System.out.println(Arrays.toString(jobs));
int lo = 1;
int hi = M;
while (lo < hi) {
int mid = lo + (hi - lo) / 2;
if (test(mid)) {
hi = mid;
} else {
lo = mid + 1;
}
}
writer.println(lo);
int reqNum = 0;
o: for (int day = 1; day <= N; day++) {
schedule.add(new ArrayList<>());
for (int j = 0; j < lo; j++) {
if (jobs[reqNum][1] > day) break;
if (jobs[reqNum][1] + D >= day) {
schedule.get(day - 1).add(jobs[reqNum][0]);
reqNum++;
}
if (reqNum == M) break o;
}
}
while (schedule.size() < N) schedule.add(new ArrayList<>());
for (ArrayList<Integer> ds : schedule) {
for (int z : ds) {
writer.print(z + " ");
}
writer.println(0);
}
writer.close();
}
static boolean test(int numMachines) {
int reqNum = 0;
for (int day = 1; day <= N; day++) {
for (int j = 0; j < numMachines; j++) {
if (jobs[reqNum][1] > day) break;
if (jobs[reqNum][1] + D >= day) {
reqNum++;
} else {
return false;
}
if (reqNum == M) return true;
}
}
return false;
}
}
