#include <bits/stdc++.h>
using namespace std;
vector<pair<int, int>> requests;
vector<vector<int>> schedule;
int n, d, m;
void buildSchedule(int machines){
int day = 0;
for(int i=0; i<m; i++){
schedule[day].push_back(requests[i].second);
if(!((i+1) % machines)){
day++;
}
}
}
bool valid(int num_machines){
int days = 0;
int cur = 0;
int time = requests[0].first;
for(auto req: requests){
if(time > req.first + d){ return 0; }
if(cur + 1 > num_machines){
days++;
time++;
cur = 0;
}
cur++;
}
if(cur) days++;
return days <= n;
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> d >> m;
schedule.resize(n);
requests.resize(m);
for(int i=0; i<m; i++){
cin >> requests[i].first;
requests[i].second = i;
}
sort(requests.begin(), requests.end());
int lo = 1, hi = m;
while(lo < hi){
int mid = lo + (hi - lo) / 2;
if(valid(mid)){
hi = mid;
} else {
lo = mid + 1;
}
}
buildSchedule(hi);
cout << hi << '\n';
for(auto day: schedule){
for(int job: day){
cout << job + 1 << ' ';
}
cout << "0\n";
}
}
