#include<bits/stdc++.h>
using namespace std;
int n,d,m;
vector<pair<int,int>>all;
bool check(int mid){
int ret=1,now=0;
for(int i=0;i<m;i++){
if(all[i].first>ret){
ret++;
now=0;
i--;
continue;
}
if(ret>all[i].first+d){
return 0;
}
now++;
if(now==mid){
ret++;
now=0;
}
}
if(now==0){
ret--;
}
if(ret>n){
return 0;
}
return 1;
}
void co(int mid){
int ret=1,now=0;
vector<vector<int>>mainres(n+1);
for(int i=0;i<m;i++){
if(all[i].first>ret){
ret++;
now=0;
i--;
continue;
}
now++;
mainres[ret].push_back(all[i].second);
if(now==mid){
ret++;
now=0;
}
}
for(int i=1;i<=n;i++){
if((int)mainres[i].size()>mid){
assert(0);
}
for(auto x:mainres[i]){
cout<<x+1<<" ";
}
cout<<0<<"\n";
}
}
long long solve(){
long long low=0,high=1e9+5,mid;
while(high-low>1){
mid=(high+low)>>1;
if(check(mid)){
high=mid;
}
else{
low=mid;
}
}
return high;
}
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin>>n>>d>>m;
all.resize(m);
for(int i=0;i<m;i++){
cin>>all[i].first;
all[i].second=i;
}
sort(all.begin(),all.end());
int res=solve();
cout<<res<<"\n";
co(res);
}
