import java.util.*;
import java.io.*;
public class jobs {
private class Pair{
int ind, v;
public Pair(int index, int val){
this.ind = index;
this.v = val;
}
}
private int n, d, m;
private int[][] arr;
private int[] toDoPerDay;
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];
toDoPerDay = new int[n+1];
int k;
sc = new StringTokenizer(br.readLine());
for (int i = 0; i < m; i++) { arr[i] = new int[]{i, k = Integer.parseInt(sc.nextToken())}; toDoPerDay[k]++;}
br.close();
Arrays.sort(arr, (a, b) -> a[1]-b[1]);
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][1] > i+1){break;}
System.out.print(arr[j][0] + 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][1] > days){
// break;
// }
// }
// } return (done==m);
int toDo = 0;
for(int i = 1; i <= (n-d); i++){
toDo += toDoPerDay[i];
toDo = Math.max(0, toDo-numMachines);
}
return (toDo == 0);
}
}
