#include <bits/stdc++.h>
using namespace std;
int n,m,d;
vector<pair<int,int>> vec;
pair<bool,vector<vector<int>>> f(int x){
vector<vector<int>> schedule(n);
int req=0;
for(int day=1;day<=n;day++){
for(int i=0;i<x;i++){
if(vec[req].first>day){
break;
}
if(vec[req].first+d >= day){
schedule[day-1].push_back(vec[req++].second);
}
else{
return make_pair(false,schedule);
}
if(req==m){
return make_pair(true,schedule);
}
}
}
return make_pair(false,schedule);
}
int main(){
cin >> n >> d >> m;
vec.resize(m);
for(int i=0;i<m;i++){
int day;
cin >> day;
vec[i] = make_pair(day,i+1);
}
sort(vec.begin(),vec.end());
vector<vector<int>> result;
int l=0,r=m;
while(l<r){
int mid = l + (r-l)/2;
pair<bool,vector<vector<int>>> cur = f(mid);
if(cur.first){
r = mid;
result = cur.second;
}
else{
l = mid+1;
}
}
cout << l << "\n";
for(int i=0;i<n;i++){
for(int j : result[i]){
cout << j << " ";
}
cout << 0 << "\n";
}
}
