/*
* Author: Nonoze
* Created: Sunday 30/06/2024
*/
#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template<class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<class T> using ordered_multiset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long ll;
#define int long long
#ifdef _IN_LOCAL
#include <bits/DebugTemplate.h>
#else
#define dbg(...)
#endif
#define sz(x) (int)(x.size())
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define pb push_back
#define mp make_pair
#define fi first
#define se second
// #define endl '\n'
#define endlfl '\n' << flush
template<typename T> void read(T& x, bool write=0) { if (write) cout << x << ' '; else cin >> x; }
template<typename T1, typename T2> void read(pair<T1, T2>& p, bool write=0) { read(p.first, write), read(p.second, write); if (write) cout << endl;}
template<typename T> void read(vector<T>& v, bool write=0) { for (auto& x : v) read(x, write); if (write) cout << endl; }
template<typename T1, typename T2> void read(T1& x, T2& y, bool write=0) { read(x, write), read(y, write); if (write) cout << endl; }
template<typename T1, typename T2, typename T3> void read(T1& x, T2& y, T3& z, bool write=0) { read(x, write), read(y, write), read(z, write); if (write) cout << endl; }
template<typename T1, typename T2, typename T3, typename T4> void read(T1& x, T2& y, T3& z, T4& zz, bool write=0) { read(x, write), read(y, write), read(z, write), read(zz, write); if (write) cout << endl; }
template<typename T> void print(T x) { read(x, 1); }
template<typename T1, typename T2> void print(T1 x, T2 y) { read(x, y, 1); }
template<typename T1, typename T2, typename T3> void print(T1 x, T2 y, T3 z) { read(x, y, z, 1); }
template<typename T1, typename T2, typename T3, typename T4> void print(T1 x, T2 y, T3 z, T4 zz) { read(x, y, z, zz, 1); }
#define quit(x) return (void)(cout << x << endl)
#define cmin(a, b) a = min(a, b)
#define cmax(a, b) a = max(a, b)
const int inf = numeric_limits<int>::max() / 4;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int MOD = 1e9+7, LOG=25;
void solve();
signed main() {
ios::sync_with_stdio(0);
cin.tie(0);
int tt=1;
// cin >> tt;
while(tt--) solve();
return 0;
}
int n, k, m;
vector<pair<int, int>> abase;
vector<vector<int>> a;
bool ok(int x) {
queue<int> todo;
for (int i=0; i<m; i++) {
for (auto u: a[i]) todo.push(i);
for (int t=0; t<x && !todo.empty(); t++) {
if (todo.back()+k<i) return 0;
todo.pop();
}
}
if (!todo.empty()) return 0;
return 1;
}
vector<vector<int>> calc(int x) {
set<pair<int, int>> todo;
vector<vector<int>> ans;
for (int i=0; i<m; i++) {
for (auto u: a[i]) todo.insert({i, u});
vector<int> now;
for (int t=0; t<x && !todo.empty(); t++) {
now.pb(todo.begin()->se+1);
todo.erase(todo.begin());
}
now.pb(0);
ans.pb(now);
}
return ans;
}
void solve() {
read(m, k, n);
a.resize(m);
for (int i=0; i<n; i++) {
int x; read(x);
a[x-1].pb(i);
}
int ans=n, l=1, r=n;
while (l<=r) {
int mid=(l+r)/2;
if (ok(mid)) ans=mid, r=mid-1;
else l=mid+1;
}
cout << ans << endl;
auto res=calc(ans);
for (auto u: res) {
for (int i=0; i<sz(u); i++) {
if (i) cout << ' ';
cout << u[i];
}
cout << endl;
}
}
