import java.util.*;
import java.lang.*;
import java.io.*;
class jobs {
static int[][] jobs;
static int n, d, m;
static List<List<Integer>> form(int count) {
List<List<Integer>> ans = new ArrayList<>();
for (int day = 1, l = 0, r = 0; day <= n; day++) {
List<Integer> cur = new ArrayList<>();
while (r < m && jobs[r][0] == day) {
r++;
}
for (int rep = 0; rep < count && l < r; rep++) {
cur.add(jobs[l++][1]);
}
cur.add(0);
ans.add(cur);
}
return ans;
}
// return true if there is a way to use `count` no. of machines to solve
static boolean ok(int count) {
for (int day = 1, l = 0, r = 0; day <= n; day++) {
while (r < m && jobs[r][0] == day) {
r++;
}
if (l < r && day - jobs[l][0] > d)
return false;
for (int rep = 0; rep < count && l < r; rep++) {
l++;
}
}
return true;
}
public static void main(String[] args) throws java.lang.Exception {
Kattio io = new Kattio();
n = io.nextInt();
d = io.nextInt();
m = io.nextInt();
jobs = new int[m][2];
for (int i = 0; i < m; i++) {
int day = io.nextInt();
jobs[i][0] = day;
jobs[i][1] = i + 1;
}
Arrays.sort(jobs, (a, b) -> Integer.compare(a[0], b[0]));
int lo = 1, hi = m, best = m;
while (lo <= hi) {
int mid = lo + (hi - lo) / 2;
if (ok(mid)) {
best = mid;
hi = mid - 1;
} else {
lo = mid + 1;
}
}
io.println(best);
for (List<Integer> row : form(best)) {
for (int x : row) {
io.print(x);
if (x != 0)
io.print(' ');
}
io.println();
}
io.close();
}
}
class Kattio extends PrintWriter {
private BufferedReader r;
private StringTokenizer st;
// standard input
public Kattio() {
this(System.in, System.out);
}
public Kattio(InputStream i, OutputStream o) {
super(o);
r = new BufferedReader(new InputStreamReader(i));
}
// USACO-style file input
public Kattio(String problemName) throws IOException {
super(problemName + ".out");
r = new BufferedReader(new FileReader(problemName + ".in"));
}
// returns null if no more input
public String next() {
try {
while (st == null || !st.hasMoreTokens())
st = new StringTokenizer(r.readLine());
return st.nextToken();
} catch (Exception e) {
}
return null;
}
public int nextInt() {
return Integer.parseInt(next());
}
public double nextDouble() {
return Double.parseDouble(next());
}
public long nextLong() {
return Long.parseLong(next());
}
}
