#include <fstream>
#include <iostream>
#include <iomanip>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <cmath>
#include <cstring>
#include <climits>
using namespace std;
using ll = long long;
const int INF = 2e5 + 5;
int n, d, m;
pair<int, int> a[INF], b[INF];
bool ok(int num_machines) {
int current_day = 1;
int current_index = 0;
while (current_index < m) {
for (int i = 0; i < num_machines && current_index < m; i++) {
if (a[current_index].first + d < current_day) {
return false;
}
current_index++;
}
current_day++;
}
return true;
}
int main()
{
ios_base::sync_with_stdio(false); cin.tie(0);
//ifstream fin(".in");
//ofstream fout(".out");
cin >> n >> d >> m;
for (int i = 0; i < m; i++) {
cin >> a[i].first;
a[i].second = i + 1;
}
sort(a, a + m);
int left = 0, right = m;
while (right > left + 1) {
int middle = (left + right) / 2;
if (ok(middle)) {
right = middle;
} else {
left = middle;
}
}
cout << right << "\n";
int count = n;
for (int i = 0; i < m; i += right) {
for (int j = i; j < min(m, i + right); j++) {
cout << a[j].second << " ";
}
count--;
cout << 0 << "\n";
}
for (int i = 0; i < count; i++) {
cout << 0 << "\n";
}
return 0;
}
/*
* 8 2 12
1 2 4 2 1 3 5 6 1 3 6 4
*/
//
