import java.io.*;
import java.util.*;
public class jobs {
static int n, d, m;
static Pair[] requests;
public static void main(String[] args) throws Exception {
FastIO fi = new FastIO(System.in);
n = fi.nextInt();
d = fi.nextInt();
m = fi.nextInt();
requests = new Pair[m];
for (int i = 0; i < m; i++) {
requests[i] = new Pair(fi.nextInt(), i + 1);
}
Arrays.sort(requests, (r1, r2) -> r1.a - r2.a);
// Binary search on the answer
int lo = 0, hi = n;
while (lo < hi) {
int mid = (lo + hi) / 2;
if (check(mid)) {
hi = mid;
} else {
lo = mid + 1;
}
}
// Print answer
System.out.println(lo);
int days = 0;
for (int i = 0; i < m; i += lo) {
days++;
int j = i;
while (j < m && j < i + lo) {
System.out.print(requests[j].b + " ");
j++;
}
System.out.println(0);
}
// Print out the remaining zeroes
while (days < n) {
days++;
System.out.println(0);
}
}
static boolean check(int delay) {
int days = 0;
for (int i = 0; i < m; i += delay) {
days++;
int j = i;
while (j < m && j < i + delay) {
if (requests[j].a + d >= days) {
j++;
} else {
return false;
}
}
}
return days <= n;
}
static class Pair {
int a, b;
public Pair(int a, int b) {
this.a = a;
this.b = b;
}
}
static class FastIO {
InputStream dis;
byte[] buffer = new byte[1 << 17];
int pointer = 0;
public FastIO(String fileName) throws Exception {
dis = new FileInputStream(fileName);
}
public FastIO(InputStream is) throws Exception {
dis = is;
}
int nextInt() throws Exception {
int ret = 0;
byte b;
do {
b = nextByte();
} while (b <= ' ');
boolean negative = false;
if (b == '-') {
negative = true;
b = nextByte();
}
while (b >= '0' && b <= '9') {
ret = 10 * ret + b - '0';
b = nextByte();
}
return (negative) ? -ret : ret;
}
long nextLong() throws Exception {
long ret = 0;
byte b;
do {
b = nextByte();
} while (b <= ' ');
boolean negative = false;
if (b == '-') {
negative = true;
b = nextByte();
}
while (b >= '0' && b <= '9') {
ret = 10 * ret + b - '0';
b = nextByte();
}
return (negative) ? -ret : ret;
}
byte nextByte() throws Exception {
if (pointer == buffer.length) {
dis.read(buffer, 0, buffer.length);
pointer = 0;
}
return buffer[pointer++];
}
String next() throws Exception {
StringBuffer ret = new StringBuffer();
byte b;
do {
b = nextByte();
} while (b <= ' ');
while (b > ' ') {
ret.appendCodePoint(b);
b = nextByte();
}
return ret.toString();
}
}
}
