#include <bits/stdc++.h>
using namespace std;
#define name "jobs"
#define MAXN 1000006
#define pb push_back
#define pf push_front
#define ll long long
#define ii pair<int, int>
#define fs first
#define sc second
#define ill pair<int, ll>
#define lli pair<ll, int>
#define llll pair<ll, ll>
#define all(v) v.begin(),v.end()
#define uni(v) v.erase(unique(all(v)),v.end())
#define bit(n,i) (((n)>>(i))&1)
#define FOR(i,a,b) for (int i=(a),_b=(b); i<=_b; i++)
#define FORD(i,a,b) for (int i=(a),_b=(b); i>=_b; i--)
#define MASK(i) (1LL<<(i))
const int INF=1e9;
const int MOD=1e9+7;
void add(int &u, int v){
u+=v;
if (u>=MOD) u-=MOD;
}
void sub(int &u, int v){
u-=v;
if (u<0) u+=MOD;
}
void minimize(int &u, int v){
u=min(u,v);
}
void maximize(int &u, int v){
u=max(u,v);
}
long long Rand(long long l, long long r){
ll tmp=0;
FOR(i,1,4) tmp=((tmp<<15)^(((1<<15)-1)&rand()));
return l+tmp%(r-l+1);
}
int n,d,m;
ii a[MAXN];
bool check(int x){
int j=1;
FOR(i,1,n){
if (j>m) break;
if (a[j].fs+d<i) return 0;
int cnt=1;
while (j<=m&&a[j].fs<=i&&cnt<=x){
++cnt;
++j;
}
}
return j>m;
}
vector<int> vec[MAXN];
int main()
{
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
cin>>n>>d>>m;
FOR(i,1,m){
cin>>a[i].fs;
a[i].sc=i;
}
sort(a+1,a+m+1);
int l=1,r=m,res=-1;
while (l<=r){
int mid=(l+r)/2;
if (check(mid)){
r=mid-1;
res=mid;
}
else l=mid+1;
}
cout<<res<<"\n";
int j=1;
FOR(i,1,n){
int cnt=1;
while (j<=m&&a[j].fs<=i&&cnt<=res){
vec[i].pb(a[j].sc);
++cnt;
++j;
}
}
FOR(i,1,n){
while (vec[i].size()){
cout<<vec[i].back()<<" ";
vec[i].pop_back();
}
cout<<0<<"\n";
}
return 0;
}
