#include <bits/stdc++.h>
using namespace std;
#define int long long
#define dl long double
#define rep(i,a,b) for (auto i = a; i <= b; ++i)
#define per(i,a,b) for (auto i = a; i >= b; --i)
#define pii pair<int,int>
#define all(v) (v).begin(), (v).end()
#define pb push_back
#define fi first
#define se second
const int MAXN = 1e5 + 10;
int a[MAXN], pfx[MAXN];
void solve() {
int n,m,d;
cin >> n >> d >> m;
vector<pii> t;
rep(i,1,m) {
int x;
cin >> x;
a[x]++;
t.pb({x,i});
}
rep(i,1,n) pfx[i] = pfx[i-1] + a[i];
sort(all(t));
int l = 1, r = m, ans = 0;
while (l <= r) {
int mid = (l+r)/2;
bool ok = true;
rep(i,1,n) {
ok &= pfx[max(i-d,0LL)] <= mid*i;
}
if (ok) {
ans = mid;
r = mid - 1;
} else {
l = mid + 1;
}
}
cout << ans << '\n';
int i = 0;
rep(cur,1,n) {
rep(j,1,ans) {
if (i == m || t[i].fi > cur) break;
cout <<t[i].se << ' ';
i++;
}
cout << "0\n";
}
}
int32_t main() {
ios_base::sync_with_stdio(0);cin.tie(nullptr);
int tt = 1;
//cin >> tt;
while (tt--) solve();
}
