#include <bits/stdc++.h>
using namespace std;
#define int long long
void solve() {
int n, d, m;
cin >> n >> d >> m;
vector<pair<int, int>> v(m);
for (int i = 0; i < m; i++) {
cin >> v[i].first;
v[i].second = i;
}
sort(v.begin(), v.end());
int ans, l = 1, r = m;
vector<vector<int>> schedule;
while (l <= r) {
int mid = (l + r) / 2;
bool good = false, bad = false;
vector<vector<int>> cur_schedule(n, vector<int>(mid, -1));
for (int i = 0; i < n; i++) {
for (int j = 0; j < mid; j++) {
if (i * mid + j == m) {
good = true;
break;
}
if (v[i * mid + j].first + d <= i) {
bad = true;
break;
}
cur_schedule[i][j] = v[i * mid + j].second;
}
if (good or bad) break;
}
if (good) {
schedule = cur_schedule, ans = mid;
r = mid - 1;
}else l = mid + 1;
}
cout << ans << "\n";
for (int i = 0; i < n; i++) {
for (int j = 0; j < ans; j++) {
if (schedule[i][j] != -1) cout << schedule[i][j] + 1 << " ";
}
cout << 0 << "\n";
}
}
int32_t main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
solve();
return 0;
}
