#include <bits/stdc++.h>
#define vi vector<int>
#define ve vector
#define ll long long
#define vf vector<float>
#define vll vector<pair<ll,ll>>
#define ii pair<int,int>
#define vvi vector<vi>
#define vii vector<ii>
#define gii greater<ii>
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define INF 1e9
#define eps 1e-7
#define eps1 1e-25
#define optimise ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define MAX_A 1e5+5
#define V 450
using namespace std;
const int MOD = 1e9+7;
const int nax = 200005;
int n,d,m;
vii s;
int main(){
cin >> n >> d >> m;
for (int i = 0; i < m; ++i)
{
int a;
cin >> a;
s.pb({a,i});
}
sort(s.begin(), s.end());
int l = 1, r = 1e6;
while(l < r){
int md=(l+r)/2;
int done = 0;
for (int i = 1; i <= n; ++i)
{
if(done == m) break;
if(i-s[done+1].fi > d){
done = -1;
break;
}
int p = upper_bound(s.begin(), s.end(),mp(i,(int)(1e7)))-s.begin();
done += min(p-done,md);
}
if(done == m){
r = md;
} else {
l = md + 1;
}
}
int res = (l+r)/2;
cout << res << endl;
int done = -1;
for (int i = 1; i <= n; ++i)
{
if(done == m){
cout << 0 << endl;
} else {
int p = upper_bound(s.begin(), s.end(),mp(i,(int)(1e7)))-s.begin();
for (int i = done+1; i <= min(min(p,res+done),m-1); ++i)
{
cout << s[i].se+1 << " ";
}
cout << 0 << endl;
done += min(p-done,res);
//cout << done << " " << p-done << endl;
}
}
}
