#include <bits/stdc++.h>
using namespace std;
int n,d,m;
pair<bool,vector<vector<int>>> works(vector<pair<int,int>> &jobs,int machines){
int temp=0;
vector<vector<int>> schedule(n);
for(int day=1;day<=n;day++){
for(int mac=0;mac<machines;mac++){
if(jobs[temp].first>day){
break;
}
if(jobs[temp].first+d>=day){
schedule[day-1].push_back(jobs[temp++].second);
}
else{
return {false,schedule};
}
if(temp==m){return {true,schedule};}
}
}
return {false,schedule};
}
int main(){
//ios::sync_with_stdio(false);
//cin.tie(0);
cin >> n >> d >> m;
vector<pair<int,int>> jobs(m);
for(int i=0;i<m;i++){
int day;
cin >> day;
//date,index
jobs[i] = {day,i+1};
}
sort(jobs.begin(),jobs.end());
vector<vector<int>> ans;
int l=0,r=m,mid;
while(l<r){
mid = l+(r-l)/2;
pair<bool,vector<vector<int>>> res = works(jobs,mid);
if(res.first){
r=mid;
ans = res.second;
}
else{
l=mid+1;
}
}
cout << l << endl;
for(int i=0;i<n;i++){
for(auto j : ans[i]){
cout << j << ' ';
}
cout << 0 << endl;
}
}
