#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define pii pair<int, int>
#define pll pair<ll, ll>
using namespace std;
#define MOD 1000000007
#define INF 10000000
int n, d, m;
vector<pii> times;
vector<vector<int>> answer;
bool check(int mp) {
queue<pii> tasks;
vector<vector<int>> order(n);
int ptr = 0;
for (int i = 0; i < n; i++) {
int curr_time = i + 1;
while (ptr < m && times[ptr].first <= curr_time) {
tasks.push(times[ptr++]);
}
for (int j = 0; j < mp; j++) {
if (tasks.empty()) break;
pii p = tasks.front();
tasks.pop();
if (p.first - curr_time > d) return false;
order[i].push_back(p.second);
}
}
if (!tasks.empty()) return false;
answer = order;
return true;
}
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
// freopen("angry.in", "r", stdin);
// freopen("angry.out", "w", stdout);
cin >> n >> d >> m;
times.resize(m);
for (int i = 0; i < m; i++) {
ll x;
cin >> x;
times[i] = {x, i};
}
sort(times.begin(), times.end());
int l = 0, r = m;
int ans = 0;
while (l <= r) {
int mp = (l + r) / 2;
if (check(mp)) {
ans = mp;
r = mp - 1;
} else l = mp + 1;
}
cout << ans << '\n';
for (int i = 0; i < n; i++) {
for (int j : answer[i]) cout << j + 1 << ' ';
cout << "0\n";
}
}
/*
8 2 12
1 2 4 2 1 3 5 6 2 3 6 4
*/
