#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define MAX 100100
int n, d, m;
pair<int, int> a[MAX];
bool f(int mid)
{
int j = 1;
for (int i = 1; i <= n; i++) {
int cnt = 0;
// cout << i << " " << j << " " << a[j].fi << endl;
while (cnt < mid && j <= m && a[j].first <= i && a[j].first + d >= i) {
cnt++;
// cout << a[j].se << " ";
j++;
}
if (j <= m && a[j].fi + d < i) return false;
}
return true;
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
cin >> n >> d >> m;
for (int i = 1; i <= m; i++) {
cin >> a[i].fi;
a[i].se = i;
}
sort(a + 1, a + m + 1);
int l = 1, r = m, res = -1;
while (l <= r) {
int mid = (l + r) >> 1;
if (f(mid)) {
res = mid;
r = mid - 1;
} else l = mid + 1;
}
cout << res << endl;
int j = 1;
for (int i = 1; i <= n; i++) {
int cnt = 0;
// cout << i << " " << j << " " << a[j].fi << endl;
while (cnt < res && j <= m && a[j].first <= i && a[j].first + d >= i) {
cnt++;
cout << a[j].se << " ";
j++;
}
cout << 0 << endl;
}
return 0;
}
