import java.util.*;
import java.io.*;
public class jobs {
private int n, d, m;
private int[][] arr;
public static void main(String[] args) throws IOException{
new jobs();
}
public jobs() throws IOException{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
StringTokenizer sc = new StringTokenizer(br.readLine());
n = Integer.parseInt(sc.nextToken());
d = Integer.parseInt(sc.nextToken());
m = Integer.parseInt(sc.nextToken());
arr = new int[m][2];
sc = new StringTokenizer(br.readLine());
for (int i = 0; i < m; i++) { arr[i] = new int[]{i+1, Integer.parseInt(sc.nextToken())};}
br.close();
Arrays.sort(arr, (a, b) -> a[1]-b[1]);
int lb = 1, ub = m, mid;
while (lb < ub){
mid = (lb+ub)/2;
if (works(mid)){ub = mid;}
else{lb = mid+1;}
}
System.out.println(lb);
int j = 0;
for(int i = 0; i < n; i++){
int end = Math.min(m, j + lb);
for(; j < end; j++){
if (arr[j][1] > i+1){break;}
System.out.print(arr[j][0] + " ");
}
System.out.println(0);
}
}
public boolean works(int numMachines){
int curMachines = numMachines, day = 1;
for(int i = 0; i < m; i++){
if (arr[i][1] > day){day = arr[i][1]; curMachines = numMachines;}
if (arr[i][1] + d < day){
return false;
}
curMachines--;
if (curMachines == 0){curMachines = numMachines; day++;}
}return true;
}
}
