#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5+5;
const int MAXM = 1e6+5;
struct job{
int ind, day;
};
int N, D, M, mesin_ans = MAXM;
job data[MAXM];
bool isJobCompleted(int mesin){
int pos = 0;
for(int i=1;i<=N;i++){
for(int j=0;j < mesin && data[pos].day <= i && pos < M;j++){
if(i > data[pos].day+D) return 0;
pos++;
}
}
return 1;
}
void print_ans(){
int pos = 0;
cout << mesin_ans << endl;
for(int i=1;i<=N;i++){
for(int j=0;j < mesin_ans && data[pos].day <= i && pos < M;j++){
cout << data[pos].ind << " ";
pos++;
}
cout << 0 << endl;
}
}
bool cmp(job a, job b){
if(a.day == b.day) return a.ind < b.ind;
return a.day < b.day;
}
int main(){
cin >> N >> D >> M;
for(int i=0;i<M;i++){
cin >> data[i].day;
data[i].ind = i+1;
}
sort(data, data+M, cmp);
int l = 1,
r = M;
while(l<=r){
int mid = (l+r)/2;
if(isJobCompleted(mid)){
mesin_ans = min(mid, mesin_ans);
r = mid-1;
}else l = mid+1;
}
print_ans();
return 0;
}
