#include <bits/stdc++.h>
using namespace std;
int n,d,m,l,r,mid,ct;
pair <int,int> a[100005];
bool ok;
int main(){
ios::sync_with_stdio(false);
cin >> n >> d >> m;
for (int i=1;i<=m;i++){
cin >> a[i].first;
a[i].second=i;
}
sort(a+1,a+1+m);
l=1; r=m;
while (l < r){
mid=(l+r)/2; ct=0;
ok=true;
for (int i=1;i<=m;i+=mid){
ct++;
for (int j=i;j<=i+mid-1;j++){
if (a[j].first+d < ct)
ok=false;
}
}
if (ok)
r=mid;
else
l=mid+1;
}
cout << l << "\n";
for (int i=0;i<n;i++){
for (int j=i*l+1;j<=min(m,i*l+l);j++){
cout << a[j].second << " ";
}
cout << "0\n";
}
return 0;
}
