import java.util.*;
import java.lang.*;
import java.io.*;
class jobs {
static int[][] jobs;
static int n, d, m;
// return non-empty result if there is a way to use `count` number of machine
// to finish all jobs under time-limit
static List<List<Integer>> ok(int count) {
List<List<Integer>> res = new ArrayList<>();
int finished = 0;
for (int day = 1, l = 0, r = 0; day <= n; day++) {
while (r < m && jobs[r][0] >= day) {
r++;
}
List<Integer> cur = new ArrayList<>();
while (l < r && cur.size() < count) {
if (day - jobs[l][0] > d) return new ArrayList<>();
cur.add(jobs[l++][1]);
finished++;
}
res.add(cur);
}
return finished < m ? new ArrayList<>() : res;
}
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).isEmpty()) {
best = mid;
hi = mid - 1;
} else {
lo = mid + 1;
}
}
io.println(best);
List<List<Integer>> ans = ok(best);
for (List<Integer> row : ans) {
for (int x : row) {
io.print(x + " ");
}
io.println(0);
}
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()); }
}
