#include<bits/stdc++.h>
using namespace std;
int n, d, m;
pair<bool, vector<vector<int> > > works(const vector<pair<int, int> > &jobs, int machineCount){
vector<vector<int> > schedule(n);
int reqNum = 0;
for (int day = 1; day <= n; day++){
for (int j = 0; j < machineCount; j++){
if (jobs[reqNum].first > day){
break;
}
if (jobs[reqNum].first + d >= day){
schedule[day - 1].push_back(jobs[reqNum++].second);
}
else{
return make_pair(false, schedule);
}
if (reqNum == m){
return make_pair(true, schedule);
}
}
}
return make_pair(false, schedule);
}
int main(){
cin >> n >> d >> m;
vector<pair<int, int> > jobs(m);
for (int i = 0; i < m; i++){
int day;
cin >> day;
jobs[i] = make_pair(day, i + 1);
}
sort(jobs.begin(), jobs.end());
vector<vector<int> > result;
int l = 1, r = m;
while (l < r){
int machineNum = (l + r) / 2;
pair<bool, vector<vector<int> > > curResult = works(jobs, machineNum);
if (curResult.first){
r = machineNum;
result = curResult.second;
}
else{
l = machineNum + 1;
}
}
cout << l << "\n";
for(int i = 0; i < n; i++){
for(int &idx : result[i]){
cout << idx << " ";
}
cout << 0 << "\n";
}
}
