#include "bits/stdc++.h"
#define sz(x) (int)size(x)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
using namespace std;
using ll = long long;
using pii = pair<int, int>;
const char nl = '\n';
const int INF = 0x3f3f3f3f;
const ll LINF = 0x3f3f3f3f3f3f3f3f;
int32_t main() {
ios::sync_with_stdio(0), cin.tie(0);
int n, d, m; cin >> n >> d >> m;
vector<vector<int>> day(n + 1);
for (int i = 1; i <= m; i++) {
int x; cin >> x;
day[x].push_back(i);
}
vector<vector<int>> res(n + 1);
auto val = [&](int k) -> bool {
queue<pii> q;
vector<vector<int>> cur(n + 1);
for (int i = 1; i <= n; i++) {
for (int x : day[i])
q.push({i, x});
for (int _ = 0; _ < k; _++) {
if (q.empty()) break;
auto [x, id] = q.front();
q.pop();
if (x + d < i) return false;
cur[i].push_back(id);
}
}
res = cur;
return true;
};
int l = 0; // l is bad
int r = m; // r is good
while (r > l + 1) {
int mid = (l + r) / 2;
val(mid) ? r = mid : l = mid;
}
cout << r << nl;
for (int i = 1; i <= n; i++) {
for (int x : res[i])
cout << x << ' ';
cout << 0 << nl;
}
return 0;
}
