/*************
the author:
shimutski_zoro
************ */
#include <bits/stdc++.h>
using namespace std;
#define yon(x) cout<<((x)?"YES":"NO");
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define ff first
#define ss second
#define em emplace_back
#define rep(i,j,k) for(int i=j;i<=k;i++)
#define per(i,j,k) for(int i=k;i>=j;i--)
#define forp(x,y,a) for(auto &[x,y]:(a))
typedef long long ll;
typedef pair<ll,ll> pll;
typedef vector<ll> vl;
typedef vector<pll> vpl;
typedef vector<vl> vvl;
typedef vector<vpl> vvpl;
typedef vector<string> vs;
typedef deque<ll> dl;
const int mod=1e9+7;
ll inf =1e18+1;
const int M=1e6;
const int N=1e3+1;
const ll dx[]={1,0,-1,0},dy[]={0,1,0,-1};
void solve(){
ll n,m,d;
cin>>n>>d>>m;
vpl a(m);
rep(i,0,m-1)cin>>a[i].ff , a[i].ss=i+1;
sort(all(a));
//forp(x,y,a)cout<<x<<" "<<y<<"\n";
function<pair<bool,vvl>(ll)>check=[&](ll r)->pair<bool,vvl>{
vvl tmp=vvl (n);
ll cnt=0;
rep(i,1,n){
rep(j,1,r){
if(a[cnt].ff>i)
break;
if(a[cnt].ff+d<i){
return {0,tmp};
}else{
tmp[i-1].em(a[cnt].ss);
cnt++;
}
if(cnt>=m)return {1,tmp};
}
}
return {0,tmp};
};
vvl v(n);
ll lo=1,hi=1e9;
ll ans=m;
while(lo<=hi){
ll mid= lo + (hi-lo)/2;
pair<bool,vvl>p=check(mid);
if(p.ff){
hi=mid-1;
ans=mid;
v=p.ss;
}else{
lo=mid+1;
}
}
cout<<ans<<endl;
//vvl v(n+1);
rep(i,0,n-1){
for(auto it:v[i]){
cout<<it<<" ";
}
cout<<0<<"\n";
}
}
signed main()
{
ios_base::sync_with_stdio(NULL);
cin.tie(nullptr);
cout.tie(nullptr);
#ifdef Usaco
string f="herding";
freopen((f+".in").c_str(),"r",stdin);
freopen((f+".out").c_str(),"w",stdout);
#endif
int t = 1;
//cin >> t;
while (t--)
{
solve();
// if(t>0)
//cout<<endl;
}
}
/*
*/
