#include <bits/stdc++.h>
using namespace std;
int n, d, m;
pair<int, int> a[1000005];
int main()
{
ios::sync_with_stdio(false); cin.tie(0);
cin >> n >> d >> m;
for (int i = 1; i <= m; ++i)
{
cin >> a[i].first;
a[i].second = i;
}
sort(a+1, a+1+m);
int lo = 0, hi = 1e6 + 1;
while (lo < hi)
{
int mid = lo + (hi - lo) / 2;
int idx = 1;
bool flag = true;
for (int i = 1; i <= n; ++i)
{
int cnt = 0;
while (idx <= m && a[idx].first <= i && cnt < mid)
{
if (i - a[idx].first > d)
{
flag = false;
break;
}
++cnt, ++idx;
}
if (!flag) break;
}
if (flag && idx >= m) hi = mid;
else lo = mid + 1;
}
if (lo > 1000000)
{
cout << -1;
return 0;
}
cout << lo << '\n';
int idx = 1;
for (int i = 1; i <= n; ++i)
{
int cnt = 0;
while (idx <= m && a[idx].first <= i && cnt < lo)
{
if (i - a[idx].first > d) break;
cout << a[idx].second << ' ';
++cnt, ++idx;
}
cout << "0\n";
}
return 0;
}
