#include <iostream>
#include <cstdio>
#include <cstring>
#include <vector>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>
using namespace std;
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
using vi = vector<int>;
using ll = long long;
using pii = pair<int, int>;
const int maxn = 1000000 + 7;
int n, d, m;
pii task[maxn];
vi day[100007];
bool check(int mid) {
rep(i, 0, n) {
day[i].clear();
}
int it = 0;
rep(i, 0, n) {
int cnt = 0;
while (it < m) {
if (task[it].f > i) break;
if (i > task[it].f + d) {
return false;
}
if (cnt < mid) {
day[i].push_back(task[it].s);
cnt++;
it++;
} else {
break;
}
}
}
return true;
}
int main() {
ios::sync_with_stdio(false);
#ifndef ONLINE_JUDGE
//freopen("angry.in", "r", stdin);
//freopen("angry.out", "w", stdout);
#endif
cin >> n >> d >> m;
rep(i, 0, m) {
cin >> task[i].f;
task[i].f--;
task[i].s = i + 1;
}
sort(task, task + m);
int l = 0, r = m + 1;
while (l < r) {
int mid = l + (r - l) / 2;
if (check(mid)) {
r = mid;
} else {
l = mid + 1;
}
}
cout << l << endl;
rep(i, 0, n) {
for (int id : day[i]) {
cout << id << " ";
}
cout << 0 << endl;
}
}
