#include <bits/stdc++.h>
using namespace std;
#ifdef DEBUG
#include "../Library/debug.h"
#else
#define dbg(x...)
#endif
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef vector<int> vi;
typedef vector<bool> vb;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define F0R(i, a) for (int i = 0; i < (a); ++i)
#define FORd(i, a, b) for (int i = (b) - 1; i >= (a); --i)
#define F0Rd(i, a) for (int i = (a) - 1; i >= 0; --i)
#define trav(a, x) for (auto& a : x)
#define f first
#define s second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) x.begin(), x.end()
const char nl = '\n';
const int INF = 1e9;
const int MOD = 1e9 + 7;
void solve(){
int n,d,m;
cin>>n>>d>>m;
vector<vi> a(n);
F0R(i,m){
int x;
cin>>x;--x;
a[x].pb(i);
}
priority_queue<pi,vpi,greater<pi>> pq;
vector<vpi> ans;
// ans.push_back(vpi());
F0R(i,n){
trav(j,a[i]){
pq.push({i,j});
}
while(!pq.empty()&&pq.top().f+d<i){
vpi tmp;
int cur=pq.top().f;
while(!pq.empty()&&pq.top().f+d>=cur&&pq.top().f<=cur&&cur<i){
dbg(cur)
auto [t,id] = pq.top();
pq.pop();
tmp.pb({cur,id});
cur=max(cur+1,pq.empty()?-1:pq.top().f);
}
dbg(i)
dbg(tmp)
ans.pb(tmp);
}
trav(j,ans){
if(!pq.empty()){
auto [t,id] = pq.top();
pq.pop();
j.pb({i,id});
}
}
}
while(!pq.empty()&&pq.top().f+d<n+1){
vpi tmp;
int cur=pq.top().f;
while(!pq.empty()&&pq.top().f+d>=cur&&pq.top().f<=cur&&cur<n+1){
auto [t,id] = pq.top();
pq.pop();
tmp.pb({cur,id});
cur++;
}
dbg(tmp)
ans.pb(tmp);
}
dbg(ans)
vector<vi> mp(n);
trav(i,ans){
trav(j,i){
mp[j.f].pb(j.s);
}
}
cout<<sz(ans)<<nl;
F0R(i,n){
trav(j,mp[i]){
cout<<j+1<<" ";
}
cout<<"0\n";
}
}
int32_t main(){
ios::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
int TC = 1;
// cin >> TC;
while(TC--){
solve();
}
return 0;
}
