#include <bits/stdc++.h>
using namespace std;
int N, D, M;
vector<int> arr[100001];
bool check(int x) {
queue<int> q;
int wait = 0;
for (int i = 1; i <= N; i++) {
for (int j = 0; j < (int)arr[i].size(); j++) {
q.push(i);
}
if (!q.empty()) {
wait = max(wait, i-q.front());
}
for (int j = 0; j < x && !q.empty(); j++) {
q.pop();
}
}
return wait <= D;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> N >> D >> M;
for (int i = 1; i <= M; i++) {
int t;
cin >> t;
arr[t].push_back(i);
}
int high = M;
int low = 0;
while (low < high) {
int mid = (high+low+1)/2;
if (check(mid)) {
high = mid-1;
}
else {
low = mid;
}
}
int ans = high+1;
cout << ans << "\n";
queue<int> q;
for (int i = 1; i <= N; i++) {
for (auto v: arr[i]) {
q.push(v);
}
for (int j = 0; j < ans && !q.empty(); j++) {
cout << q.front() << ' ';
q.pop();
}
cout << 0 << '\n';
}
}
