import java.util.*;
public class jobs{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int d = sc.nextInt();
int m = sc.nextInt();
Pair[] arr = new Pair[m];
for (int i = 0; i < m; i++) { arr[i] = new Pair(i, sc.nextInt()); }
sc.close();
Arrays.sort(arr, (a, b) -> a.compareTo(b));
int ans = (int) Math.ceil(m/(double)(n-d));
System.out.println(ans);
int j = 0;
for(int i = 0; i < n; i++){
int end = Math.min(m, j + ans);
for(; j < end; j++){
if (arr[j].v > i+1){break;}
System.out.print(arr[j].ind + 1 + " ");
}
System.out.println(0);
}
}
}
class Pair{
int ind, v;
public Pair(int index, int val){
this.ind = index;
this.v = val;
}
public int compareTo(Pair p){
return this.v - p.v;
}
}
