#include <bits/stdc++.h>
using namespace std;
const int nx = 1e5 + 5;
vector<int> add[nx], qrs[nx];
int n, d, m;
int main() {
ios_base::sync_with_stdio(0), cin.tie(0);
cin >> n >> d >> m;
for (int i = 1; i <= m; i++) {
int x; cin >> x;
add[x].emplace_back(i);
qrs[x + d + 1].emplace_back(i);
}
// search from 1 -> n + 1
int l = 1, r = m;
while (l < r) {
int mid = (l + r) / 2;
queue<int> q;
bool del[10*nx];
memset(del, 0, sizeof del);
bool ok = 1;
for (int i = 1; i <= n + 1; i++) {
for (auto idx : qrs[i]) {
if (!del[idx]) {
ok = 0;
//cout << mid << " " << idx << "\n";
break;
}
}
if (!ok) break;
for (auto idx : add[i]) q.emplace(idx);
int ct = 0;
//cout << i << " : ";
while (!q.empty() && ct < mid) {
ct++;
del[q.front()] = 1;
//cout << q.front() << " ";
q.pop();
}
//cout << endl;
}
if (ok) r = mid;
else l = mid + 1;
}
vector<int> ans[n + 1];
cout << l << "\n";
queue<int> q;
for (int i = 1; i <= n; i++) {
for (auto idx : add[i]) q.emplace(idx);
int ct = 0;
while (!q.empty() && ct < l) {
ct++;
ans[i].push_back(q.front());
q.pop();
}
for (auto idx : ans[i]) {
cout << idx << " ";
}
cout << 0 << "\n";
}
}
/*
8 2 12
1 2 4 2 1 3 5 6 2 3 6 4
2
5 1 0
9 4 0
2 10 0
6 12 0
3 7 0
11 8 0
0
0
*/
