#include <bits/stdc++.h>
using namespace std;
vector<vector<int>> tasks;
int N, D, M;
vector<vector<int>> possible (int nbMachine) {
queue <pair<int,int>> q;
vector<vector<int>> ans(N);
for (int i(0); i < N; i++) {
if (!q.empty() && i - q.front().second > D) return {};
int sum = nbMachine;
for (int x : tasks[i]) q.push({x, i});
while (!q.empty() && sum > 0) {
sum--;
ans[i].push_back(q.front().first);
q.pop();
}
}
if (!q.empty()) return {};
return ans;
}
int main() {
cin.tie(0);
ios::sync_with_stdio(false);
cin >> N >> D >> M;
tasks.resize(N);
for (int i = 0; i < M; i++) {
int a; cin >> a; a--;
tasks[a].push_back(i + 1);
}
int l = 0, r = 1000000;
while (l < r) {
int mid = r - (r - l) / 2;
//cout << l << " " << r << '\n';
if (possible(mid).empty()) l = mid;
else r = mid - 1;
}
cout << l + 1 << '\n';
vector<vector<int>> ans = possible(l + 1);
for (auto x : ans) {
for (int y : x) {
cout << y << " ";
}
cout << "0\n";
}
return 0;
}
