#include<bits/stdc++.h>
using namespace std;
pair<int, int> p[1000005];
int N, D, M;
bool check(int machines){
int m[machines];
memset(m,0,sizeof(m));
int index = 0;
for (int i = 0; i < N; i++){
if (index == machines){
index = 0;
}
m[index] = max(m[index]+1,p[i].first+1);
if (m[index] > p[i].first+D){
return false;
}
index++;
}
return true;
}
int main(){
cin >> N >> D >> M;
for (int i = 0; i < M; i++){
cin >> p[i].first;
p[i].second = i+1;
}
sort(p,p+M);
int l = 0;
int r = M;
while (l != r){
int mid = (l+r)/2;
if (check(mid)){
r = mid;
}
else{
l = mid+1;
}
}
cout << l << endl;
int ntracker = 0;
int index = 0;
while(true){
if (ntracker == N){
break;
}
for (int j = 0; j < l; j++){
if (index == M){
break;
}
cout << p[index].second << " ";
index++;
}
cout << 0 << endl;
ntracker++;
}
}
