#include <bits/stdc++.h>
using namespace std;
const int MAX=1e6+10;
const int N=1e5+10;
pair<long long,long long> niza[MAX];
long long n,d,m;
vector<long long> ress[N];
bool work(int mid)
{
if(mid<=0)return false;
if(mid>=m)return true;
int i=0;
for(int day=1; day<=n; day++)
{
ress[day].clear();
for(int j=0; j<mid; j++)
{
if(i>=m)break;
if(niza[i].first>day)break;
if(niza[i].first+d<day)return false;
ress[day].push_back(niza[i].second);
i++;
}
}
return (i>=m);
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cin>>n>>d>>m;
for(long long i=0; i<m; i++)
{
cin>>niza[i].first;
niza[i].second=i+1;
}
sort(niza,niza+m);
long long b=0,e=m;
long long res=0;
while(b<e)
{
long long mid=(b+e)/2;
bool flag=work(mid);
if(flag)
{
res=mid;
e=mid;
}
else b=mid+1;
}
cout<<res<<endl;
work(res);
for(int i=1; i<=n; i++)
{
for(auto x:ress[i])cout<<x<<" ";
cout<<0<<endl;
}
return 0;
}
/*
8 2 12
1 2 4 2 1 3 5 6 2 3 6 4
*/
