#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
int n, d, m;
pair <int, int> arr[1000001] = {};
bool check (int x) {
int pos = 1;
int days = 0;
while (pos <= m) {
pair <int, int> dd = arr[pos];
dd.F += d;
int new_pos = upper_bound(arr + 1, arr + m + 1, dd) - arr;
new_pos--;
new_pos = min(new_pos, m);
new_pos = min(new_pos, pos + x - 1);
days++;
pos = new_pos + 1;
}
return (days <= n);
}
void build (int x) {
int pos = 1;
int days = 0;
while (pos <= m) {
pair <int, int> dd = arr[pos];
dd.F += d;
int new_pos = upper_bound(arr + 1, arr + m + 1, dd) - arr;
new_pos--;
new_pos = min(new_pos, m);
new_pos = min(new_pos, pos + x - 1);
days++;
for (int i = pos; i <= new_pos; i++) cout << arr[i].S << " ";
cout << 0 << endl;
pos = new_pos + 1;
}
while (days <= n) {
cout << 0 << endl;
days++;
}
}
int main () {
cin >> n >> d >> m;
for (int i = 1; i <= m; i++) {
cin >> arr[i].F;
arr[i].S = i;
}
sort(arr + 1, arr + m + 1);
int l = 1, r = m;
int mid, ans = m;
while (l <= r) {
mid = (l + r) >> 1;
if (check(mid)) {
r = mid - 1;
ans = mid;
} else {
l = mid + 1;
}
}
cout << ans << endl;
build(ans);
}
