#include <bits/stdc++.h>
#define int long long
#define debug cout << "ok\n";
#define SQR(x) (1LL * ((x) * (x)))
#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define pii pair<int,int>
#define pli pair<ll,int>
#define vi vector<int>
#define FAST ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef unsigned int ui;
using namespace std;
const int M = 1e9 + 7;
const int INF = 1e9 + 7;
const ll INFLL = (ll)2e18 + 7LL;
const ld PI = acos(-1);
const int dx[] = {1, -1, 0, 0, -1, 1, 1, -1};
const int dy[] = {0, 0, 1, -1, -1, -1, 1, 1};
template<class _, class __>
bool minimize(_ &x, const __ y){
if(x > y){
x = y;
return true;
} else return false;
}
template<class _, class __>
bool maximize(_ &x, const __ y){
if(x < y){
x = y;
return true;
} else return false;
}
template<class _,class __>
void Add(_ &x, const __ y) {
x += y;
if (x >= M) {
x -= M;
}
return;
}
template<class _,class __>
void Diff(_ &x, const __ y) {
x -= y;
if (x < 0) {
x += M;
}
return;
}
//--------------------------------------------------------------
const int MaxN = 1e6+7;
int m,d,n,res;
pii a[MaxN];
vi lis[MaxN];
bool check(int ans) {
for (int i=1;i<=m;i++) lis[i].clear();
queue<int> q;
for (int i=1,j=1;i<=m;i++) {
while (j <= n && a[j].fi <= i) {
q.push(j);
j++;
}
if (!q.empty() && a[q.front()].fi + d < i) return false;
for (int k=1;k<=ans && !q.empty();k++) {
lis[i].pb(a[q.front()].se);
q.pop();
}
}
return q.empty();
}
void sol() {
cin >> m >> d >> n;
for (int i=1;i<=n;i++) {
cin >> a[i].fi;
a[i].se = i;
}
sort(a+1,a+n+1);
int l = 1, r = n;
while (l <= r) {
int mid = (l+r) >> 1;
if (check(mid)) {
res = mid;
r = mid - 1;
}
else l = mid + 1;
}
check(res);
cout << res << '\n';
for (int i=1;i<=m;i++) {
for (int x : lis[i]) cout << x << ' ';
cout << 0 << '\n';
}
}
signed main() {
// freopen("test.inp","r",stdin);
// freopen("test.out","w",stdout);
FAST
int t=1;
// cin >> t;
while (t--) sol();
}
