#include<bits/stdc++.h>
using namespace std;
const int MAXN=1e6+5;
vector<int> vi[MAXN/10],aa[MAXN/10];
int cnt[MAXN];
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n,d,m;
cin>>n>>d>>m;
for(int i=1;i<=m;i++)
{
int res;
cin>>res;
vi[res].push_back(i);
}
int l=1,r=m,ans=0;
while(l<=r)
{
int mid=(l+r)/2,pt=n;
for(int i=1;i<=n;i++) cnt[i]=vi[i].size();
for(int i=n;i;i--)
{
if(pt>i) break;
int c=0;
while(pt>=i-d&&pt>0&&c<mid)
{
while(cnt[pt]>0&&c<mid) cnt[pt]--,c++;
if(cnt[pt]==0) pt--;
}
}
if(!pt) r=mid-1,ans=mid;
else l=mid+1;
}
cout<<ans<<"\n";
int pt=n;
for(int i=n;i;i--)
{
int c=0;
while(pt>=i-d&&pt>0&&c<ans)
{
while(!vi[pt].empty()&&c<ans) aa[i].push_back(vi[pt][vi[pt].size()-1]),vi[pt].pop_back(),c++;
if(vi[pt].empty()) pt--;
}
}
for(int i=1;i<=n;i++)
{
for(auto v:aa[i]) cout<<v<<" ";
cout<<"0\n";
}
}
