// I will become better someday.
#include <bits/stdc++.h>
using namespace std;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
typedef pair <int, int> pii;
typedef pair <ll, int> pli;
typedef pair <int, ll> pil;
typedef pair <ll, ll> pll;
typedef pair <ld, ld> pdd;
#define debug(x) cout << '[' << #x << ": " << x << "] "
#define cio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define cases int _; cin >> _; while(_--)
#define pb push_back
#define eb emplace_back
#define space << " " <<
#define lb lower_bound
#define ub upper_bound
#define F first
#define S second
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define Unique(v) v.erase(unique(all(v)), v.end())
#define mset(x) memset(x, 0, sizeof(x))
#define sflush fflush(stdout)
#define cflush cout.flush()
#define yes cout << "YES\n"
#define no cout << "NO\n"
#define lyes cout << "Yes\n"
#define lno cout << "No\n"
#define nl cout << "\n";
#define vt vector
#define ar array
#define uid uniform_int_distribution
template <typename T>
istream& operator >> (istream& in, vector<T>& a){
for(auto &x : a) in >> x;
return in;
}
template <typename T>
ostream& operator << (ostream& out, vector<T>& a){
for(auto &x : a) out << x << ' ';
return out;
}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng64(chrono::steady_clock::now().time_since_epoch().count());
ll read(){
int w = 1, c;
ll ret;
while((c = getchar()) > '9' || c < '0'){
w = (c == '-' ? -1 : 1);
}
ret = c - '0';
while((c = getchar()) >= '0' && c <= '9'){
ret = ret * 10 + c - '0';
}
return ret * w;
}
ll rd(){
ll in;
cin >> in;
return in;
}
void write(ll x){
if(x < 0){
putchar('-');
x = -x;
}
if(x > 9){
write(x / 10);
}
putchar(x % 10 + '0');
}
const int MAXN = 3e5 + 5, MAXM = 2e5 + 5, INF = 1e9 + 5, MOD = 1e9 + 7;
const ll LMOD = (ll) 1e18 + 9;
const ll LINF = 1e18 + 5;
const ld ep = 1e-8, Pi = acos(-1.0);
int n, m, k, x, d;
int a[MAXN];
string s;
void clear(){
}
int main(){
cio;
cin >> n >> d >> m;
vector<vector<int>> rec(n + 1);
for (int i = 1; i <= m; ++i) {
cin >> a[i];
rec[a[i]].pb(i);
}
auto check = [&](int x) -> bool {
queue<int> q;
for (int i = 1; i <= n; ++i) {
for (int j : rec[i]) q.push(j);
for (int j = 1; j <= x && !q.empty(); ++j) {
q.pop();
}
if (!q.empty() && a[q.front()] + d <= i) return 0;
}
return 1;
};
int l = 1, r = m, res = -1;
while (l <= r) {
int mid = (l + r) >> 1;
if (check(mid)) {
res = mid;
r = mid - 1;
}
else l = mid + 1;
}
cout << res << "\n";
queue<int> q;
for (int i = 1; i <= n; ++i) {
for (int j : rec[i]) q.push(j);
for (int j = 1; j <= res && !q.empty(); ++j) {
cout << q.front() << " ";
q.pop();
}
cout << 0 << "\n";
}
return 0;
}
