// In the name of God
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
template <class T> using indexed_set = tree<T, null_type, less<T>,
rb_tree_tag, tree_order_statistics_node_update>;
#define watch(x) cerr << "{" << (#x) << " = " << x << "}" << '\n';
#define watch2(x, y) cerr << "{" << (#x) << " = " << x << ", " << (#y) << " = " << y << "}" << '\n';
#define watch3(x, y, z) cerr << "{" << (#x) << " = " << x << ", " << (#y) << " = " << y << ", " << (#z) << " = " << z << "}" << '\n';
#define fast_io ios::sync_with_stdio(false); cin.tie(0), cout.tie(0);
const ll maxn = 1e6 + 10, INF = 1e9;
int n, d, m;
pii a[maxn];
vector<vector<int>> ans(n);
bool ok (int x)
{
ans.clear();
ans.resize(n+10);
multiset<int> s;
for (int i = 0; i < x; i++)
s.insert(1);
for (int i = 0; i < m; i++) {
auto it = s.upper_bound(a[i].first + d);
if (it == s.begin()) {
if (*it - a[i].first > d)
return false;
}
else
it--;
assert(it != s.end());
int f = *it;
s.erase(it);
s.insert(max(f, a[i].first) + 1);
ans[max(f, a[i].first)].push_back(a[i].second);
}
return true;
}
int main()
{
fast_io
cin >> n >> d >> m;
for (int i = 0; i < m; i++) {
cin >> a[i].first;
a[i].second = i+1;
}
sort(a, a + m);
int l = 0, r = 1e6;
while (r > l + 1) {
int mid = (r + l) / 2;
if (ok(mid)) r = mid;
else l = mid;
}
cout << r << '\n';
for (int i = 1; i <= n; i++) {
for (int x : ans[i]) {
cout << x << ' ';
}
cout << 0 << '\n';
}
return 0;
}
