#include <bits/stdc++.h>
using namespace std;
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
long long n,d,m;
cin>>n>>d>>m;
pair<long long,long long> niza[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+1;
long long res=0;
vector<long long> ress[n+1],v[n+1];
while(b<=e)
{
long long mid=(b+e)/2;
if(mid==0)
{
b=mid+1;
continue;
}
int i=0;
bool flag=true;
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)
{
flag=false;
break;
}
ress[day].push_back(niza[i].second);
i++;
}
if(!flag)break;
}
if(flag)
{
res=mid;
e=mid-1;
}
else b=mid+1;
}
cout<<res<<endl;
int i=0;
for(int day=1; day<=n; day++)
{
ress[day].clear();
for(int j=0; j<res; j++)
{
if(i>=m)break;
if(niza[i].first>day)break;
ress[day].push_back(niza[i].second);
i++;
}
}
for(long long 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
*/
