#include <bits/stdc++.h>
#define pii pair<int, int>
using namespace std;
const int MAX = 100007;
vector<int> S[MAX], X[MAX];
bool Check(int Z, int N, int D) {
for (int i = 1; i <= N; ++i) {
X[i].clear();
X[i].shrink_to_fit();
}
queue<pii> Q;
for (int i = 1; i <= N; ++i) {
for (int n : S[i]) Q.emplace(i + D, n);
int t = min(Z, (int)Q.size());
while (t--) {
auto [d, id] = Q.front(); Q.pop();
if (d < i) return 0;
X[i].push_back(id);
}
}
return Q.empty();
}
int main() {
ios::sync_with_stdio(0); cin.tie(0);
int N, D, M;
cin >> N >> D >> M;
for (int i = 1; i <= M; ++i) {
int n;
cin >> n;
S[n].push_back(i);
}
int L = 0, R = M;
while (L + 1 < R) {
int mid = (L + R) >> 1;
(Check(mid, N, D) ? R : L) = mid;
}
Check(R, N, D);
cout << R << '\n';
for (int i = 1; i <= N; ++i) {
for (int n : X[i]) cout << n << ' ';
cout << 0 << '\n';
}
return 0;
}
