#include <bits/stdc++.h>
#define ll long long
using namespace std;
int main() {
ios::sync_with_stdio(0), cin.tie(0);
int n, d, m; cin >> m >> d >> n;
pair <int, int> a[n];
int id = 1;
for (auto &[x, y] : a) cin >> x, y = id++;
sort(a, a+n);
int cnt[m+1]; memset(cnt, 0, sizeof(cnt));
vector <int> ans[m+1];
multiset <pair <int, int>> ms;
int L = 1, R = 0;
for (auto &[x, y] : a) {
while (R < x+d && R < m) {
R++;
ms.emplace(0, R);
}
while (L < x) {
ms.erase(ms.find(make_pair(cnt[L], L)));
L++;
}
auto [c, id] = *ms.begin();
ms.erase(ms.begin());
ans[id].emplace_back(y);
cnt[id]++;
ms.emplace(cnt[id], id);
}
int x = 0;
for (int i = 1; i <= m; i++) x = max(x, cnt[i]);
cout << x << '\n';
for (int i = 1; i <= m; i++) {
for (auto &e : ans[i]) cout << e << ' ';
cout << 0 << '\n';
}
}
