// Source: https://usaco.guide/general/io
#include <bits/stdc++.h>
using namespace std;
int main() {
cin.tie(0)->sync_with_stdio(false);
int n, d, m;
cin >> n >> d >> m;
vector<pair<int, int>> t(m);
for (int i = 0; i < m; i++) {
cin >> t[i].first;
t[i].second = i + 1;
}
sort(t.begin(), t.end());
vector<vector<int>> res;
int l = 0, r = m;
while (l + 1 < r) {
int mid = l + (r - l) / 2;
vector<vector<int>> cur(n + 1);
queue<int> q;
for (int i = 0; i < mid; i++) {
q.push(0);
}
bool works = true;
for (int i = 0; i < m; i++) {
if (q.front() - d <= t[i].first) {
int jt = max(q.front(), t[i].first);
q.push(jt + 1);
cur[jt].push_back(t[i].second);
q.pop();
} else {
works = false;
break;
}
}
if (works) {
r = mid;
res = cur;
} else {
l = mid;
}
}
cout << r << endl;
for (int i = 1; i <= n; i++) {
for (int x : res[i]) {
cout << x << " ";
}
cout << 0 << endl;
}
}
