import java.util.*;
import java.lang.*;
import java.io.*;
class jobs {
static List<Integer[]> jobs;
static int n, d, m;
static void form(int count) {
for (int day = 1, l = 0, r = 0; day <= n; day++) {
while (r < m && jobs.get(r)[0] == day) {
r++;
}
for (int rep = 0; rep < count && l < r; rep++) {
out.print(jobs.get(l++)[1]);
out.print(' ');
}
out.println(0);
}
}
// 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.get(r)[0] == day) {
r++;
}
if (l < r && day - jobs.get(l)[0] > d)
return false;
for (int rep = 0; rep < count && l < r; rep++) {
l++;
}
}
return true;
}
public static void solve() {
n = ni();
d = ni();
m = ni();
jobs = new ArrayList<Integer[]>();
for (int i = 0; i < m; i++) {
int day = ni();
jobs.add(new Integer[] { day, i + 1 });
}
Collections.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;
}
}
out.println(best);
form(best);
}
/* I/O Template from uwi */
static InputStream is;
static PrintWriter out;
static String INPUT = "";
static String taskName = null;
public static void main(String[] args) throws Exception {
long S = System.currentTimeMillis();
if (taskName != null) {
File initialFile = new File(taskName + ".in");
is = new FileInputStream(initialFile);
out = new PrintWriter(taskName + ".out");
} else {
is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
out = new PrintWriter(System.out);
}
solve();
out.flush();
long G = System.currentTimeMillis();
tr(G - S + "ms");
}
private static boolean eof() {
if (lenbuf == -1)
return true;
int lptr = ptrbuf;
while (lptr < lenbuf)
if (!isSpaceChar(inbuf[lptr++]))
return false;
try {
is.mark(1000);
while (true) {
int b = is.read();
if (b == -1) {
is.reset();
return true;
} else if (!isSpaceChar(b)) {
is.reset();
return false;
}
}
} catch (IOException e) {
return true;
}
}
private static byte[] inbuf = new byte[1024];
static int lenbuf = 0, ptrbuf = 0;
private static int readByte() {
if (lenbuf == -1)
throw new InputMismatchException();
if (ptrbuf >= lenbuf) {
ptrbuf = 0;
try {
lenbuf = is.read(inbuf);
} catch (IOException e) {
throw new InputMismatchException();
}
if (lenbuf <= 0)
return -1;
}
return inbuf[ptrbuf++];
}
private static boolean isSpaceChar(int c) {
return !(c >= 33 && c <= 126);
}
private static int skip() {
int b;
while ((b = readByte()) != -1 && isSpaceChar(b))
;
return b;
}
private static double nd() {
return Double.parseDouble(ns());
}
private static char nc() {
return (char) skip();
}
private static String nline() {
int b = skip();
StringBuilder sb = new StringBuilder();
while (b != '\n') { // when nextLine, (isSpaceChar(b) && b != ' ')
sb.appendCodePoint(b);
b = readByte();
}
return sb.toString();
}
private static String ns() {
int b = skip();
StringBuilder sb = new StringBuilder();
while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != ' ')
sb.appendCodePoint(b);
b = readByte();
}
return sb.toString();
}
private static char[] ns(int n) {
char[] buf = new char[n];
int b = skip(), p = 0;
while (p < n && !(isSpaceChar(b))) {
buf[p++] = (char) b;
b = readByte();
}
return n == p ? buf : Arrays.copyOf(buf, p);
}
private static char[][] nm(int n, int m) {
char[][] map = new char[n][];
for (int i = 0; i < n; i++)
map[i] = ns(m);
return map;
}
private static int[] na(int n) {
int[] a = new int[n];
for (int i = 0; i < n; i++)
a[i] = ni();
return a;
}
private static int ni() {
int num = 0, b;
boolean minus = false;
while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
;
if (b == '-') {
minus = true;
b = readByte();
}
while (true) {
if (b >= '0' && b <= '9') {
num = num * 10 + (b - '0');
} else {
return minus ? -num : num;
}
b = readByte();
}
}
private static long nl() {
long num = 0;
int b;
boolean minus = false;
while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
;
if (b == '-') {
minus = true;
b = readByte();
}
while (true) {
if (b >= '0' && b <= '9') {
num = num * 10 + (b - '0');
} else {
return minus ? -num : num;
}
b = readByte();
}
}
private static void tr(Object... o) {
if (INPUT.length() != 0)
System.out.println(Arrays.deepToString(o));
}
}
