//#include "gondola.h"
#include <bits/stdc++.h>
#define pb push_back
#define pf push_front
using namespace std;
#define F first
#define S second
typedef long long ll;
#define pii pair <int, int>
#define pll pair <ll, ll>
typedef long double ld;
const ll N = 1e6 + 100, M = 1e7 + 10, len = 21, inf = 1e18;
const ll mod = 1000000009LL;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
ll um(ll a, ll b){
return (1LL * a * b) % mod;
}
ll subr(ll a, ll b){
return ((1LL * a - b) % mod + mod) % mod;
}
ll n, d, from = 0, m;
pll a[N];
vector <vector <ll>> vec;
bool check(ll x){
ll st = 1;
for(ll i = 1; i <= n; i++){
if((ll)vec.size() - from >= d) return 0;
vector <ll> cur;
while(st <= m){
if(a[st].F == i){
cur.pb(a[st].S);
st++;
} else break;
}
vec.pb(cur);
ll xx = x;
while(xx--){
while(from < (ll)vec.size()){
if(vec[from].size() == 0) from++;
else break;
}
if(from >= (ll)vec.size()) break;
vec[from].pop_back();
while(from < (ll)vec.size()){
if(vec[from].size() == 0) from++;
else break;
}
}
}
if(from == (ll)vec.size()) return true;
return false;
}
void make(ll x){
ll st = 1;
for(ll i = 1; i <= n; i++){
vector <ll> cur;
while(st <= m){
if(a[st].F == i){
cur.pb(a[st].S);
st++;
} else break;
}
vec.pb(cur);
ll xx = x;
while(xx--){
while(from < (ll)vec.size()){
if(vec[from].size() == 0) from++;
else break;
}
if(from >= (ll)vec.size()) break;
cout << vec[from].back() << " ";
vec[from].pop_back();
while(from < (ll)vec.size()){
if(vec[from].size() == 0) from++;
else break;
}
}
cout << 0 << endl;
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> d >> m;
for(int i = 1; i <= m; i++){
cin >> a[i].F;
a[i].S = i;
}
sort(a + 1, a + 1 + m);
ll l = 0, r = m;
while(r - l > 1){
ll mid = (l + r) / 2;
vec.clear();
from = 0;
if(check(mid)) r = mid;
else l = mid;
}
cout << r << endl;
make(r);
return 0;
}
