#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define v vector
#define all(x) x.begin(),x.end()
#define pii pair<int,int>
#define f first
#define s second
int main(){
int n,d,m;
cin>>n>>d>>m;
v<pii>t(m);
for(int i=0;i<m;i++){
cin>>t[i].f;
t[i].s=i+1;
}
sort(all(t));
int lo=1,hi=n,sol=n;
while(lo<hi){
int mid=(hi-lo)/2,cnt=0;
int day=1,cur=0;
for(int i=0;i<m;i++){
if(t[i].f<=day&&day<=t[i].f+d){
cnt++;
cur++;
}
if(cur==mid){
cur=0;
day++;
}
}
if(cnt<n){
lo=mid;
}
else{
hi=mid-1;
sol=min(sol,mid);
}
}
int day=1,cur=0;
v<v<int> >each_day(n+1);
for(int i=0;i<m;i++){
if(t[i].f<=day&&day<=t[i].f+d){
cur++;
each_day[day].pb(t[i].s);
}
if(cur==sol){
cur=0;
day++;
}
}
cout<<sol<<endl;
for(int i=1;i<=n;i++){
if(!each_day[i].size()){
cout<<"0\n";
continue;
}
for(int j:each_day[i]){
cout<<j<<' ';
}
cout<<"0\n";
}
}
