#include <bits/stdc++.h>
using namespace std;
#define fastio ios_base::sync_with_stdio(0); cin.tie(0)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define ll long long
struct P{
ll x, y;
};
void dbg_out() { cerr << endl; }
template <typename H, typename... T>
void dbg_out(H h, T... t) { cerr << ' ' << h; dbg_out(t...); }
#define dbg(...) { cerr << #__VA_ARGS__ << ':'; dbg_out(__VA_ARGS__); }
signed main(){
fastio;
int n, d, m;
cin >> n >> d >> m;
vector<pair<int, int>> arr (m);
for (int i=1, x; i<=m; i++){
cin >> x;
arr[i-1] = {x, i};
}
sort(all(arr));
int l=1, r=m, pcs=1;
while (l<=r){
int mid = l + (r-l)/2;
bool late = false;
int j=0;
for (int i=0; i<n; i++){
for (int k=0; k<mid && j<m && i+1>=arr[j].first; k++, j++){
if (i+1 > arr[j].first+d){
late = true;
break;
}
}
}
if (j == m && !late){
r = mid-1;
pcs = mid;
}
else l = mid+1;
}
cout << pcs << '\n';
int j=0;
for (int i=0; i<n; i++){
for (int k=0; k<pcs && j<m && i+1>=arr[j].first; k++, j++){
cout << arr[j].second << ' ';
}
cout << 0 << '\n';
}
}
