import java.util.*;
public class jobs {
private 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;
}
}
private int n, d, m;
private Pair[] arr;
public static void main(String[] args) {
new jobs();
}
public jobs(){
Scanner sc = new Scanner(System.in);
n = sc.nextInt();
d = sc.nextInt();
m = sc.nextInt();
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 lb = 0, 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].v > i+1){break;}
System.out.print(arr[j].ind + 1 + " ");
}
System.out.println(0);
}
}
public boolean works(int numMachines){
int done = 0;
for(int days = 1; days<=(n-d); days++){
int end = Math.min(m, done+numMachines);
for (;done<end;done++){
if (arr[done].v > days){
break;
}
}
} return (done==m);
}
}
