#include <bits/stdc++.h>
//#include "incursion.h"
using namespace std;
#define ll long long
void upsolve(){
int n,m,d;
cin>>n>>d>>m;
vector<int> a(m+1,0);
vector<pair<int,int>> mas;
for(int i=1;i<=m;++i){
cin>>a[i];
mas.push_back({a[i],i});
}
sort(a.begin(),a.end());
sort(mas.begin(),mas.end());
int l=1;
int r=m;
int answ=m;
while(l<=r){
int mid=(l+r)/2;
bool fl=1;
int day=1;
int cnt=0;
for(int i=1;i<=m;++i){
if(cnt==mid){
++day;
}
while(day<a[i]){
++day;
cnt=0;
}
if(day>a[i]+d){
fl=0;
break;
}
cnt++;
}
if(fl){
r=mid-1;
answ=mid;
}
else{
l=mid+1;
}
}
cout<<answ<<'\n';
for(int i=0;i<n;++i){
for(int j=i*answ;j<min(m,(i+1)*answ);++j){
cout<<mas[j].second<<' ';
}
cout<<0<<'\n';
}
}
int main(){
cin.tie(NULL);
cout.tie(NULL);
ios_base::sync_with_stdio(false);
int t;
t=1;
while(t--){
upsolve();
}
return 0;
}
